U.S. air strikes are easing the passage of Libyan forces as they seek to clear Islamic State from the militant group's former North African stronghold of Sirte, a senior field commander said on Wednesday.

Mohamed Darat said the first strikes, which took place on Monday, had helped Libyan brigades under his command secure the Dollar residential neighborhood by targeting militants who had been holding out on the district's edge.

Libya's U.N.-backed government requested the strikes nearly three months into a campaign that had slowed due to heavy casualties from sniper fire, mines and mortars.

"In the last two houses in this area we faced strong resistance so we asked (the U.S.) to hit that site," said Darat, speaking from a part of Dollar captured last week. "We moved back and they struck."