TRIPOLI, Libya — Libyan rebels claimed to be in control of most of the Libyan capital today after their lightning advance on Tripoli heralded the fall of Moammar Gadhafi’s nearly 42-year regime. Scattered battles erupted, and the mercurial leader’s whereabouts remained unknown.

The international community called on Gadhafi to step down and moved ahead with post-war planning as euphoric residents celebrated in the Green Square, the symbolic heart of the Gadhafi regime. Colleagues warned he wouldn’t go easily. Two of his sons were captured late Sunday.

The Western alliance promised to maintain its air campaign until all pro-Gadhafi forces surrender or return to barracks. NATO warplanes have hit at least 40 targets in and around Tripoli in the past two days — the highest number on a single geographic location since the bombing started more than five months ago, officials said.

The ability of rebels to move into Tripoli in an hours-long blitz showcased the evolution of the opposition fighters who first rose against the regime six months ago, swiftly capturing the eastern part of the vast North African nation but failing to advance westward toward Tripoli even with the help of months of NATO airstrikes.

For months, the rebels — mainly civilian volunteers who took up arms and had little military training — were judged to be big on zeal but short on organization and discipline, but their stunning success in Tripoli showed a high level of planning, coordination and discipline.

In London, British Prime Minister David Cameron said frozen Libyan assets would soon be released to help the country’s rebels establish order, saying Gadhafi’s regime was “falling apart and in full retreat.”

Rebel spokesman Mohammed Abdel-Rahman, who was in Tripoli, warned of pockets of resistance and said as long as Gadhafi remains on the run the “danger is still there.”

Clashes broke out early today at Gadhafi’s longtime command center known as Bab al-Aziziya when government tanks emerged from the complex and opened fire at rebels trying to get in, according to Abdel-Rahman and a neighbor. An AP reporter at the nearby Rixos Hotel heard gunfire and loud explosions from the direction of the complex.

Moammar al-Warfali, whose family home is next to the compound, said there appeared to be only a few tanks belonging to the remaining Gadhafi forces that have not fled or surrendered.

“When I climb the stairs and look at it from the roof, I see nothing at Bab al-Aziziya,” he said. “NATO has demolished it all and nothing remains.”

The Rixos also remained under the control of Gadhafi forces, with two trucks loaded with anti-aircraft machine guns and pro-regime fighters and snipers posted behind trees. Rebels and Tripoli residents set up checkpoints elsewhere in the city.

The rebels’ top diplomat in London, Mahmud Nacua, said opposition forces controlled 95 percent of Tripoli. He vowed “the fighters will turn over every stone to find” Gadhafi and make sure he faced justice.

A rebel field commander said reinforcements were arriving in Tripoli by sea from the north, south and southeast.

“Our fighters are coming from all directions and, God willing, today we will liberate the whole city,” the commander, Suleiman Sifaw, told The Associated Press.