The incident took place early Tuesday morning, when two sisters Yakta and Fareshta were on their way to a training institute in Herat city when two unknown men riding a motorbike spared acid on them.
The two sisters claimed that they were also threatened and followed by unknown men several times in the past.
Father of the two girls say they have threated many times and they referred to Police to take action about the issue.
But, Police say the perpetrators have escaped and investigations are underway for identifying and arresting them.
Several Afghan women, mostly schoolgirls, were attacked with acid in their faces by motorcycle riders, for which, the Taliban and other extremist groups were blamed in the past years.