An Afghan official says 11 soldiers have been killed in an ambush by Taliban insurgents in a western province that borders Iran.

Hesanullah Hayat, the spokesman for the governor of Herat province, said Monday that an Afghan army convoy was on its way to neighboring Bagdhis province when the attack took place on Sunday.

He says a large group of Taliban was involved in the attack.

The region has seen increase in insurgent activity since the Taliban launched their warm-weather offensive in late April.

Attacks across the country have forced the Afghan security forces to spread ever thinner, leading to an increase in the number of casualties suffered by army and police, who also fight on the front lines.