Explosion in Afghan mosque leaves casualties, witnesses say

Witnesses say a powerful explosion in a mosque in northern Afghanistan has left several casualties

KABUL, Afghanistan -- A powerful explosion in a mosque in northern Afghanistan on Friday has left several casualties, witnesses said.

The blast occurred in a Shiite mosque in Kunduz province during the weekly Friday prayer service. Witnesses said they were praying when they heard the explosion.

The cause was not immediately clear.

The Taliban leadership has been grappling with a growing threat from the local Islamic State affiliate, known as the Islamic State in Khorasan. IS militants have ramped up attacks to target their rivals, including two deadly bombings in Kabul.