Muammar Gaddafi has apparently vanished after Libyan rebels claimed to be in control of most of Tripoli following their lightning advance on the capital.
The international community called on Gaddafi to step down and moved ahead with post-war planning as euphoric residents celebrated in the Green Square, the symbolic heart of the Gaddafi regime.
Colleagues warned he would not go easily, although two of his sons were captured.
"The real moment of victory is when Gaddafi is captured," the head of the opposition's National Transitional Council, Mustafa Abdel-Jalil, said.
A top American diplomat said his whereabouts were unknown, but the US Defence Department believed he was still in the country.
Nato promised to maintain its air campaign until all pro-Gaddafi forces surrender or return to barracks. Nato planes 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.
Revellers in Tripoli flashed the "V" for victory sign and motorists circled the square honking horns and waving rebel flags.
The rest of the city, a metropolis of some two million people, was on edge, with most stores closed and large areas appearing lifeless, without even a sign of the thousands of rebels now in the city.
The rapid rebel advance into Tripoli in an hours-long blitz demonstrated the evolution of the opposition fighters who first rose against the regime six months ago, swiftly capturing the eastern part of the vast country but failing to advance westward toward Tripoli even with the help of months of Nato airstrikes.
Clashes broke out early today at Gaddafi's command centre known as Bab al-Aziziya when government tanks emerged from the complex and opened fire at rebels trying to get in.
Moammar al-Warfali, whose family home is next to the compound, said there appeared to be only a few tanks belonging to the remaining Gaddafi 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 hotel where foreign journalists are staying also remained under the control of Gaddafi 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.
Britain's Defence Secretary Liam Fox said resistance was coming mainly from foreign mercenaries, rather than Libyans still loyal to Gaddafi. "There is a certain amount of violence still occurring, we also know that a lot of the resistance from the pro-Gaddafi forces has in fact come from mercenary elements," he said.
The rebels' top diplomat in London, Mahmud Nacua, said opposition forces controlled 95% of Tripoli. He vowed "the fighters will turn over every stone to find" Gaddafi and make sure he faced justice.
A rebel field commander said reinforcements were arriving in Tripoli by sea from the north, south and south-east.
"Our fighters are coming from all directions and, God willing, today we will liberate the whole city," the commander, Suleiman Sifaw, said.
Opposition fighters captured Gaddafi's son and one-time heir apparent, Saif al-Islam, who along with his father faces charges of crimes against humanity at the International Criminal Court in the Netherlands. Another son, Mohammed, was under house arrest.
Abdel-Jalil, the rebel chief, vowed Monday to give Gaddafi a "fair trial with all legal guarantees" when captured.
Gaddafi's former right-hand man, who defected last week to Italy, said the longtime leader would not go easily.
"I think it's impossible that he'll surrender," Abdel-Salam Jalloud said, adding that "He doesn't have the courage, like Hitler, to kill himself."
Jalloud, who was Gaddafi's closest aide for decades before falling out with the leader in the 1990s, fled Tripoli on Friday.