Islamic State making 'last stand' in Libya's Sirte: Pentagon

Islamic State (IS) group militants are making a "last stand" in their former Libyan stronghold of Sirte, where they now control only about two blocks, the Pentagon said on Thursday.

The militant group had held all of the Mediterranean port city, which it captured in early 2015, establishing a significant foothold in Libya.

The United States started a bombing campaign in August at the request the UN-supported Libyan Government of National Accord (GNA) to help local forces recapture the city more than a year after the IS group seized it.

Although the operation has taken months longer than initially expected, anti-IS forces have pushed back the group's control to about 50 buildings.

The remaining militants are few in number "but they are persistent and fighting to the death," Pentagon spokesman Navy Captain Jeff Davis said. "It's a stubborn area."

"This is ISIL's last stand in Sirte and they are fighting hard," he added, using another acronym for IS.

In the capital Tripoli, clashes between armed groups escalated on Thursday night leading to the death of at least seven people south of the city, according to media reports.

The French foreign Ministry issued a statement saying France was "very worried by the escalation of violence between armed groups in Tripoli", Reuters reported.

Militia groups that hold power across the city clash frequently, but the shooting was heavier than usual and tanks and armed convoys could be seen in some areas.

Since Muammar Gaddafi's fall in a war in 2011, Libya has slipped steadily into factional fighting among brigades of former rebels who first battled the strongman and then turned against each another. IS profited from the security vacuum.

The fall of Sirte - the hometown of Gaddafi located 450km east of Tripoli - would represent a significant blow to the militant group, which has also faced a series of setbacks and major assaults in Syria and Iraq.

US warplanes, drones and helicopters have conducted 467 strikes since the air operation began in August.

The amphibious assault ship USS Wasp and its contingent of aircraft, which were involved in earlier strikes, left the region in October and continuing strikes are being conducted by drones.