Heavy fighting raged in several parts of Tripoli early Tuesday as forces loyal to Moammar Gadhafi clashed with rebel forces, even as the rebels appeared to be in control of much of the Libyan capital.

The whereabouts of the longtime Libyan leader remain unknown but the U.S. said it had no reason to believe that he had left Libya.

One of Gadhafi's sons, Seif al-Islam, who the rebels had previously claimed was under arrest, showed up early Tuesday at a hotel in Tripoli where foreign journalists have been staying. He then took reporters on a drive through parts of the city that are still under the regime's control. The convoy ended up outside Gadhafi's headquarters compound, where the Associated Press reported that at least 100 men were waiting in lines for guns to be distributed.

Earlier, gunfire and explosions could be heard around the Gadhafi compound and in a few other areas of Tripoli. Pro-Gadhafi forces managed to launch a Scud missile from near the city of Sirte, U.S. defence officials said. It wasn't clear where it landed.

"The real moment of victory is when Gadhafi is captured," said rebel National Transitional Council chief Mustafa Abdel Jalil, who was once the Libyan leader's justice minister before defecting.

Jalil said during a press confence in the eastern city of Benghazi that he hoped Gadhafi, who has ruled Libya for 42 years, would be taken alive, and that he would be given a fair trial if he was.

Tank fire

Rebel spokesman Mohammed Abdel-Rahman said that tanks emerged from Gadhafi's complex, known as Bab al-Aziziya, early Monday and began firing.

The clashes came after rebel forces made a swift advance into the capital city Sunday — a major gain that came after months of battles between rebels and Gadhafi loyalists struggling to hold other key cities and strategic sites, including oil installations and ports.

The breakthrough was the culmination of a closely co-ordinated plan by rebels, NATO and anti-Gadhafi residents inside Tripoli, rebel leaders said. Rebel fighters from the west swept over 30 kilometres in a matter of hours Sunday, taking town after town and overwhelming a major military base as residents poured out to cheer them, the Associated Press reported.

Rebels entered the city and pushed through to Green Square, the symbolic heart of the capital city. By Monday, rebels controlled large swaths of Tripoli but pockets of resistance remained.

Mahmud Nacua, the rebels' top diplomat in London, said rebel forces controlled 95 per cent of the city. He said "the fighters will turn over every stone to find [Gadhafi]" and bring him to justice.

Abdel-Rahman said that Gadhafi troops remain a threat to rebels, noting that as long as Gadhafi remains on the run the "danger is still there."

As fighting continued in Tripoli, residents tried to stay safe.

"We cannot feel peace, we cannot feel victory, until we see Gadhafi captured," said Suad Shariff, a professor at Tripoli's Libyan University, who spent the night in her home. "After Gadhafi is captured...[the people who are following him] will believe this is the end."

After more than four decades in power, there were increasing signs that Gadhafi's regime was finished:

• Two of Gadhafi's sons — Mohammed and Saadi — are reported to have been detained or captured by rebel forces.
• Libyan state television was reported to have gone off the air.
• Egypt, Libya's neighbour, recognized the National Transitional Council.

World reacts

Prime Minister Stephen Harper told reporters in Ottawa on Monday that last March, when Canada made the decision to participate in the NATO mission under the leadership of the UN, the aim was to protect Libyans against the deadly Gadhafi regime.

"Today, Canada pays tribute to the news of the beginning of the fall of the Gadhafi regime," Harper said. "We hope that the transfer of power to the National Transition Council in Libya will also be caried out peacefully.

"Libyans have expected this for a long time now. They wish to be freed of the violent, barbaric regime of Gadhafi."

Harper added that Canada's military personnel will remain in Libya, and "we will be consulting our allies as to the next stage."

Harper later spoke to the chairman of the Libyan National Transitional Council, Mustafa Abdel Jalil. The Prime Minister's Office says both men agreed that the Gadhafi regime appeared to be collapsing.

Moammar Gadhafi's whereabouts are not known. (Max Rossi/Reuters)

U.S. President Barack Obama, speaking from Martha's Vineyard, Mass., said the situation in Libya remained fluid and uncertain. But he said it was clear that Gadhafi's regime was "coming to an end, and the future of Libya is in the hands of its people."

Obama also urged the Libyan opposition to work towards a democratic government that is "peaceful, inclusive and just" and warned rebels not to seek justice through violent reprisals.

U.K. Prime Minister David Cameron called on Gadhafi to unconditionally cease fighting. Cameron also called on the Libyan rebels to respect human rights and to avoid reprisals, and said frozen assets belonging to the Libyan people would soon be released.

A European Union spokesperson said sanctions against the Libya government would remain in place for now, but that the EU was prepared to drop them quickly.

"As soon as we judge that the time is right to help the population, we will change them," EU spokesman Michael Mann said.

Italian Foreign Minister Franco Frattini echoed Cameron's call for Gadhafi to give up.

"The time is up," Frattini said. "There is no alternative to surrendering and handing himself in to justice."

'The time is up. There is no alternative to surrendering and handing himself in to justice.'—Franco Frattini, Italian foreign minister

Meanwhile, a NATO official said air patrols would continue until forces loyal to Gadhafi surrender or return to their bases. NATO warplanes hit about 40 targets around Tripoli over the past two days — the most concentrated attacks on a single area since NATO began bombing Libyan targets more than five months ago.

NATO's Secretary-General Anders Fogh Rasmussen said earlier Monday that the Libyan regime is "clearly crumbling."

Speaking in New York, UN Secretary General Ban Ki-moon said the UN has been planning for several months to assist in the reconstruction of Libya.

"The UN stands ready to provide all possible assistance to the Libyan people," he said.

Mahmoud Jibril, the international face of the rebels, urged Libyans to come together in the days ahead. Speaking on Al-Jazeera on Sunday, he also urged people to behave responsibly and avoid seeking retribution from Gadhafi loyalists.

"We need to find out why we were mistreated in the last 42 years and this can only happen if there is a genuine chance for every prisoner to be held accountable in a just trial," he was quoted as saying.

Arab uprisings

Rebels have been fighting forces loyal to Gadhafi since the uprising began in February, against a backdrop of popular revolutions across the Arab world.

Early battles in the Libyan civil war focused on areas in the rebel-dominated east, such as the cities of Brega and Ajdabiya.

After consolidating their positions in the east, the rebels closed in on Tripoli from there and from Misrata, their foothold in the largely government-held western half of the country.

On March 27, NATO began a bombing campaign against Gadhafi, following a UN Security Council resolution. On July 15, delegates from more than 30 countries, including Canada, declared Gadhafi's regime no longer legitimate, officially recognizing his main opposition — the National Transitional Council — as the country's governing authority.

With files from The Associated Press