Pakistan's military rescued five telecommunications workers kidnapped by Islamist militants last month close to the Afghan border in a series of operations in which two soldiers were killed, the military said on Friday.

Northwest Pakistan's border regions have become relatively peaceful after years of violence but Pakistani Taliban militants have been more active recently amid concern that surging violence in Afghanistan will spill over the frontier.

No group claimed responsibility for the kidnapping of 16 men installing a mobile telephone tower in the Kurram ethnic Pashtun tribal district on June 26.

Ten of the workers were later released but one man was beheaded and the militants demanded a ransom for the last five.

"To rescue the remaining 5 abducted labourers, security forces launched series of intelligence based operations in highly inhospitable terrain under extreme weather conditions," the military said in a statement.

The rescue was on Thursday. The military did not say which militants group it believed was behind the kidnapping but said civilians in the area fully supported "the security forces in fighting the menace of terrorism".

Communities along the border have recently been holding rallies to call on the government to protect them from Pakistani Taliban militants who over the past year have formed an alliance with other outlawed groups.

The militants have launched a series of attacks on the Pakistani security forces, government officials and suspected collaborators, as well as kidnapping and extorting money, government officials say.

Three soldiers were killed when militants attacked a checkpost near the border on July 5. The Pakistani Taliban, or Tehrik-e-Taliban Pakistan (TTP), claimed responsibility.

Pakistan has said the Pakistani militants could take advantage of growing instability in Afghanistan and operate along the border more freely as the Afghan Taliban take ground from government forces.

Afghanistan has for years accused the Pakistani military of providing covert support for the Afghan Taliban. Pakistan denies that.