KABUL: The Taliban said on Friday they had captured Afghanistan's biggest border crossing with Iran, as the insurgents continued a blistering offensive across the country.

"The port of Islam Qala is now under our full control and we will try to put it back in operation today," Zabihullah Mujahid, a spokesman for the insurgents, told AFP.

There was no immediate confirmation of the border crossing's fall from the government, and the Taliban's claim could not be independently verified.

Islam Qala is one of the major ports in Afghanistan, through which Kabul conducts most of its official trade with Iran.

It is the second key border crossing the insurgents have captured since they launched a sweeping offensive in early May as US-led foreign forces began their final withdrawal.

Afghan hospital burns after attack; Taliban seize border post in north

Last month the Taliban captured Shir Khan Bandar, Afghanistan's main border crossing with Tajikistan, after fierce fighting that saw hundreds of Afghan troops flee over to the neighbouring country.