Libyan forces resumed a ground attack on Sunday against Islamic State militants encircled in their former stronghold of Sirte, losing at least six of their fighters, according to a field hospital casualty list.

 

The list named six killed fighters, three of them from the city of Misrata.

 

The forces also said that the bodies of at least 10 slain Islamic State militants had been counted. The report could not be verified.

 

Forces dominated by fighters from Misrata and aligned with Libya's U.N.-backed government have been battling to capture Sirte for more than four months.

 

Supported since Aug. 1 by U.S. air strikes, they have taken control of most of the city and have been besieging militants trapped in a thin residential strip near Sirte's seafront for several weeks.

 

Their advance has been slowed by Islamic State snipers, improvised explosive devices and suicide bombings in close quarter street battles. Occasional ground attacks are interspersed by rest periods that allow fighters to regroup and hospitals to clear casualties.

 

The Misrata-led forces said in a statement posted on social media that they had conducted air sorties in preparation for a ground offensive on Sunday in Sirte's neighborhood Number Three.

 

As of Friday, the United States said it had carried out a total of 177 air strikes against Islamic State in Sirte.