TRIPOLI — British warplanes struck a large bunker in Moammar Gadhafi’s hometown of Sirte, his largest remaining stronghold, today as NATO turned its attention to loyalist forces battling advancing Libyan rebels in the area.

The airstrikes came a day after fierce clashes erupted in the Libyan capital. The rebels said pro-Gadhafi forces were still shelling the airport and sporadic shooting was reported elsewhere, but the streets of Tripoli were relatively calm today.

Rebels are trying to occupy Sirte but expect fierce resistance from tribesman and townspeople loyal to Gadhafi.

The rebel leadership, apparently trying to avoid the bloodshed that occurred in the battle for Tripoli, is working behind the scenes to secure the peaceful surrender of Sirte, Libyan rebel officials have said.

But the latest NATO airstrikes on loyalist vehicles defending Sirte appeared aimed at paving the way for the rebel advance if a negotiated settlement proves impossible.

In London, British Defense Secretary Liam Fox said some elements of Gadhafi’s regime were in Sirte “where they are still continuing to wage war on the people of Libya.” He said NATO would continue to strike at the Gadhafi forces’ military capability.

“The regime needs to recognize that the game is up,” Fox said.

Maj. Gen. Nick Pope, a British military spokesman, said royal Air Force jets also hit a large headquarters bunker in Sirte with a salvo of air-to-surface missiles.

NATO also bombed surface-to-air missile facilities near Tripoli, a statement said. Officials say Gadhafi’s forces are trying to reconstitute their anti-aircraft weapons to pose a threat to humanitarian and civilian flights into Tripoli airport.

A rebel field commander in Tripoli, Sathi Shneibi, claimed the airport was largely under opposition control but Gadhafi’s forces were shelling it from a nearby military base that had been controlled by Gadhafi’s son Khamis.

The rebels, meanwhile, were searching for the remnants of pro-Gadhafi forces in buildings in the Abu Salim neighborhood, which saw some of the heaviest fighting on Thursday.