Russian and Syrian jets struck the rebel-held city of Idlib in northern Syria on Sunday, military sources said, as President Bashar al-Assad vowed to crush insurgents who had swept into the city of Aleppo, Reuters reported.

Residents said one attack on the second day of raids hit a crowded residential area in the centre of Idlib, the largest city in a rebel enclave near the Turkish border where around four million people live in makeshift tents and dwellings.

At least seven people were killed and dozens injured, according to rescuers at the scene. The Syrian army and its ally Russia say they target the hideouts of insurgent groups and deny attacking civilians.

On Saturday, Russian and Syrian jets bombed other towns in Idlib province, which had fallen completely under rebel control in the boldest rebel assault for years in a civil war where front lines had largely been frozen since 2020.

Insurgents swept into the city of Aleppo, east of Idlib province, on Friday night, forcing the army to redeploy in the biggest challenge to Assad in years.

In remarks published on state media, Assad said: "terrorists only know the language of force and it is the language we will crush them with".

The Syrian army said dozens of its soldiers had been killed in the attack on Aleppo.

On Sunday, the army said it had recaptured several towns that had been overrun in recent days by rebels. The insurgents are a coalition of Turkey-backed mainstream secular armed groups along with Hayat Tahrir al-Sham, an Islamist group that is the opposition's most formidable military force, read the report.

Hayat Tahrir al-Sham is designated a terrorist group by the U.S., Russia, Turkey and other states.

The war, which has killed hundreds of thousands of people and displaced many millions, has ground on since 2011 with no formal end. But most major fighting halted years ago after Iran and Russia helped Assad's government win control of most land and all major cities.

Inside Aleppo city, streets were mostly empty and many shops were closed on Sunday as scared residents stayed at home. There was still a heavy flow of civilians leaving the city, witnesses and residents said.

Armed rebel fighters waving the opposition flag drove through the city, Yusuf Khatib, a resident, told Reuters by phone. Some rebels took up positions on street intersections, he added.

Ahmad Tutenji, a merchant in the affluent New Aleppo neighbourhood, said he was surprised how quickly the army left. "I am shocked at how they fled and abandoned us."

Abdullah al Halabi, a pensioner whose neighbourhood was bombed near the central area of Qasr al Baladi, said people were terrified they would see a repeat of the Russian-led bombing that killed thousands of people before driving out rebels a decade ago.

Syrian troops who had withdrawn from the city were now regrouping and reinforcements were also being sent to help in the counter-attack, army sources said.

Aleppo had been firmly held by the government since a 2016 victory there, one of the war's major turning points, when Russian-backed Syrian forces besieged and laid waste to rebel-held eastern areas of what had been the country's largest city.

Rebels said on Sunday they had pushed further south of Aleppo city and captured the town of Khansir in an attempt to cut the army's main supply route to Aleppo city.

Rebel sources said they had also captured Sheikh Najjar estate, one of the country's major industrial zones.

Reuters could not independently confirm the battlefield accounts.

Iran sent thousands of Shi'ite militias to Syria during the Syrian war and, alongside Russia with its air power, enabled Assad to crush the insurgency and regain most of his territory, Reuters reported.

A lack of that manpower to help thwart the rebel onslaught in recent days contributed to the speedy retreat of Syrian army forces, according to two army sources. Militias allied to Iran, led by Hezbollah, have a strong presence in the Aleppo area.

Israel has also in recent months stepped up its strikes on Iranian bases in Syria while also waging an offensive in Lebanon which it says has weakened Hezbollah and its military capabilities.

Syrian rebels opposed to President Bashar al-Assad said on Friday they had reached the heart of the northern city of Aleppo, after a surprise sweep through government-held towns and nearly a decade after having been forced out of the city.

The opposition fighters, led by group Hayat Tahrir al-Sham, launched an incursion on Wednesday into a dozen towns and villages in the northern province of Aleppo, which was controlled by Syrian President Bashar al-Assad's government, backed by both Iran and Russia, Reuters reported.

They made quick progress and by late Friday, an operations room representing the offensive said rebels were sweeping through various neighbourhoods of the city.

Assad and his allies Russia, Iran and regional Shi'ite militias had retaken all of Aleppo city in late 2016, with insurgents agreeing to withdraw after months of bombardment and siege in a battle that turned the tide against the opposition.

Rebel commander in the Jaish al-Izza rebel brigade Mustafa Abdul Jaber said the speedy advance was due to insufficient Iran-backed manpower in the broader province. Iran's allies in the region have suffered a series of blows at the hands of Israel as the Gaza war expanded to the Middle East.

Opposition sources in touch with Turkish intelligence say Turkey had given a green light to the offensive.

But Turkish foreign ministry spokesperson Oncu Keceli said Turkey sought to avoid greater instability in the region and had warned that recent attacks undermined de-escalation agreements.

The attack was the biggest since March 2020, when Russia and Turkey agreed to a deal to de-escalate the conflict.

CIVILIANS KILLED IN FIGHTING

Syrian state television denied rebels had reached the city and said Russia was providing Syria's military with air support.

The Syrian military said it continued to confront the attack, saying in a statement it had inflicted heavy losses on the insurgents in the countryside of Aleppo and Idlib.

David Carden, U.N. Deputy Regional Humanitarian Coordinator for the Syria Crisis, said: "We’re deeply alarmed by the situation unfolding in northwest Syria."

"Relentless attacks over the past three days have claimed the lives of at least 27 civilians, including children as young as eight years old," he told Reuters.

"Civilians and civilian infrastructure are not targets and must be protected under International Humanitarian Law."

Syrian state news agency SANA said four civilians including two students were killed on Friday in Aleppo by insurgent shelling of university student dormitories.

It was not clear if they were among the 27 dead reported by the U.N. official.

Russian and Syrian warplanes bombed the area near the border with Turkey on Thursday to try to push back an insurgent offensive that has captured territory for the first time in years, Syrian army and rebel sources said.

Kremlin spokesman Dmitry Peskov said Moscow regarded the rebel attack as a violation of Syria's sovereignty and wanted the authorities to act fast to regain control.

"As for the situation around Aleppo, it is an attack on Syrian sovereignty and we are in favour of the Syrian authorities bringing order to the area and restoring constitutional order as soon as possible," said Peskov.

Asked about unconfirmed Russian Telegram reports that Assad had flown into Moscow for talks with Russian President Vladimir Putin, Peskov said he had "nothing to say" on the matter.

European and Iranian diplomats meet on Friday to discuss whether they can engage in serious talks in the coming weeks to defuse tensions in the region, including over Tehran's disputed nuclear programme, before Donald Trump's return to the White House.

The meetings in the Swiss city of Geneva, where world powers and Iran achieved a first breakthrough in nuclear talks more than a decade ago before reaching a deal in 2015, are the first since the U.S. election, and aim to see whether any momentum can be built ahead of Jan. 20, when Trump is inaugurated, Reuters reported.

Iran's deputy foreign minister and senior nuclear negotiator Majid Takhteravanchi meets with top diplomats from Britain, Germany and France, known as the E3, on Friday, having met the EU's chief coordinator on Thursday evening.

The level of distrust between both sides was highlighted when the E3 countries on Nov. 21 pushed ahead with a resolution against Iran that tasked the U.N. atomic watchdog with preparing a "comprehensive" report on Iran's nuclear activities by the spring of 2025 despite last ditch, but limited Iranian pledges to curb uranium enrichment.

That makes the Geneva meetings more of a brainstorming session focused on their mutual concerns over how Trump will handle the dossier, diplomats said.

European, Israeli and regional diplomats say his planned administration, which includes notable Iran hawks such his Secretary of State pick Marco Rubio, will push a "maximum pressure" policy that would aim to bring Iran to its knees economically just like he attempted during his first presidency.

They also say he may seek a sort of grand bargain involving regional players to resolve the multitude of crises in the region.

The E3, the European parties to the 2015 deal, have adopted a tougher stance on Iran in recent months, notably since Tehran ramped up its military support to Russia for its war in Ukraine. However, they have always insisted that they wanted to maintain a policy of pressure and dialogue.

Three Iranian officials said Tehran’s primary objective will be finding ways to secure "lifting of sanctions” imposed since 2018, after then-President Trump reneged on the 2015 nuclear deal between Iran and six world powers.

"The establishment has decided to overcome the nuclear impasse... the goal is to use the Geneva meeting to find common ground and if we progress, Washington could join at a later stage," said one of the three officials.

GOOD FAITH

Since 2018, Iran has accelerated its nuclear programme while limiting the International Atomic Energy Agency's ability to monitor it.

"There isn't going to be an agreement until Trump takes office or any serious talks about the contours of a deal," said Kelsey Davenport, director of non-proliferation policy at the Arms Control Association advocacy group.

"But the Europeans should press Iran about what aspects of its nuclear programme it's willing to negotiate on and what security conditions in the region will need to shift for Iran to make nuclear concessions."

A European official said the primary aim was to try to agree a calendar timeline and framework to embark on good faith talks so that there is a clear commitment from Iranians to begin negotiating something concrete before Trump arrives.

Officials from both sides say the nuclear issue is just one aspect of the talks that will also address Tehran's military relationship with Russia and its regional role as fears mount that tensions between Iran and arch-rival Israel could ignite an all-out war, already volatile due to conflicts in Gaza and Lebanon and tit-for-tat strikes between the two rivals.

On announcing a ceasefire in Lebanon on Tuesday, Prime Minister Benjamin Netanyahu said the decision was made in part to turn Israel's focus to Iran.

While Trump's return to power leaves many questions open, four European diplomats said the E3 countries felt it was vital to engage now because time was running out.

Western powers hope Iran will decide to begin negotiating on new restrictions on its nuclear activities, albeit less far-reaching ones than those from 2015 with a view to having a deal by the summer.

In return sanctions would begin to be lifted, although the most damaging sanctions to Iran's economy come from Washington.

With Iran having taken its uranium enrichment far beyond the deal's limits, it is unclear whether Trump would back negotiations aimed at setting new limits before those in the 2015 deal are lifted on "termination day" in October of next year.

If no new limits are agreed before then, the report could be used to strengthen the case for so-called "snapback", a process under the 2015 deal where the issue is sent to the U.N. Security Council and sanctions lifted under the deal can be reimposed.

Iran, which has long said its nuclear programme is peaceful, has warned that it would review its nuclear doctrine if that happened.