TRIPOLI — Militants claiming allegiance to “Islamic State” fought forces loyal to Libya’s two rival governments in the central city of Sirte and further east in Benghazi, state media and military officials said on Wednesday.

In Sirte, ISIS militants killed five members of a force loyal to the government that controls Tripoli, a Tripoli-based news agency said. The United Nations and military sources said the attack near a power station on Sirte’s outskirts was a suicide bombing.

Fighters loyal to the Tripoli government, sent to Sirte from the western city of Misrata, have clashed with the militants and had set up checkpoints near the power station.

There was also heavy fighting between Islamists and forces loyal to Libya’s internationally recognized government, which is based in the east in Benghazi, after ISIS militants claimed credit for a suicide attack on an army post in the city.

“These suicide attacks show the expanding arm of terrorism that is targeting all sides and that all Libyans stand against,” the U.N. said in a statement.

War planes attacked suspected Islamist positions early on Wednesday, residents and military officials said. Gunfire and rocket propelled grenades could be heard.

Military officials had vowed air attacks on Islamists in response to a suicide bombing on Tuesday which killed seven people in Benghazi. Two more people had been killed by a rocket hitting residential buildings.

Militants claiming ties to ISIS have exploited the turmoil in Libya, where two governments and parliaments fight for control four years after the ousting of Muammar Gaddafi.