WATCH: Saif al-Islam, a son of Muammar Qaddafi and onetime heir apparent, appeared in front of cheering supporters in Tripoli early today, defying rumors that he had been captured by rebel forces. (Video by AP)
In what appears to be the first hint of the outline of a post-Qaddafi Libya, Mustafa Abdul Jalil, the leader of the opposition National Transitional Council, has called on rebel forces to show maximum restraint and discipline as they push for complete control over the capital, Tripoli.
Jalil declared that the "era of Qaddafi is over," even as pockets of pro-Qaddafi supporters continued to offer resistance in the capital and in other cities.
The embattled 69-year-old ruler's whereabouts also remained unknown, although the U.S. Defense Department said it believed that Qaddafi had not left Libya.
As opposition supporters celebrated in the streets around the country, Jalil warned Libyans that they must realize that the coming period will not be a "bed of roses."
"I call upon all Libyans to practice self-control and to protect the lives and properties of others, Libyans and others, and to refuse to take justice into their own hands outside of the framework of the law," Jalil said.
He said there was work to be done to establish the principles of freedom, equality, justice, democracy, and transparency, which inspired the Libyan revolution.
Qaddafi spokesman Moussa Ibrahim claimed there were still 65,000 troops in the city fighting for Qaddafi. Qaddafi has called on tribal supporters to join the battle and stop the rebel advance.
Meanwhile, the regime's state-controlled television has gone off the air, and opposition fighters say they are now in control of the facility in Tripoli.
What began as a popular protest movement six-months ago now appears to be on the verge of ending Qaddafi's 42-year rule.
Photo Gallery: Libyans Take To The Streets To Celebrate Rebels' Advance
Euphoric crowds across Libya have been celebrating the victory.
'Qaddafi Should Go'
The rebel gains have been met by a fresh chorus of world leaders calling on Qaddafi to relinquish power.
U.S. President Barack Obama said: "As the regime collapses, there's still fierce fighting in some areas and we have reports of regime elements threatening to continue fighting.
"Although it's clear that Qaddafi's rule is over, he still has the opportunity to reduce further bloodshed by explicitly relinquishing power to the people of Libya and calling for those forces that continue to fight to lay down their arms for the sake of Libya."
Obama also said Washington would stay in "close coordination" with the rebels to support the establishment of a democratic Libya.
He also said the United States would support the National Transitional Council with the $37 billion in assets of the Qaddafi government that were frozen earlier this year.
Addressing the Libyan people directly, he said, "The Libya that you deserve is within your reach."
Earlier in the day, British Prime Minister David Cameron also called on Qaddafi to step down.
"We have no confirmation of Qaddafi's whereabouts, but at least two of Qaddafi's sons have been detained," Cameron said. "His regime is falling apart and is in full retreat. Qaddafi must stop fighting, without conditions, and clearly show that he has given up any claim to control Libya."
The British government said it was now clear that the "end is near" for Qaddafi, and that he "must go now to avoid any further suffering for his own people."
"I would like to see Colonel Qaddafi face justice for his crimes," Cameron said earler. "He has committed appalling crimes against his own people, but Libya is a sovereign country, it is a matter for the new authorities in Libya to do what they believe is right with Qaddafi."
In Italy, Foreign Minister Franco Frattini said Qaddafi's "time is up" and that he should turn himself into the International Criminal Court. Poland, current EU president, said it welcomed the end of Qaddafi's rule.
UN Secretary-General Ban Ki-moon also called for an orderly transition and pledged support. He said that he would hold meeting on Libya later this week with major organizations, including the Arab League, the African Union, and European Union.
NATO, which has backed the rebels with a bombing campaign, has vowed to keep up its campaign until all pro-Qaddafi forces surrender or return to their barracks.
The alliance said its warplanes hit at least 40 targets in and around Tripoli in the past two days -- the highest number on a single area since the bombing began more than five months ago.
"Now is the time to create a new Libya -- a state based on freedom, not fear; democracy, not dictatorship; the will of the many, not the whims of a few," said NATO Secretary-General Anders Fogh Rasmussen in Brussels. "That transition must come peacefully. It must come now. And it must be led and defined by the Libyan people."
"The New York Times" reported U.S. drone activity in and around Tripoli had increased in recent days.
Overnight, more and more people took to the streets of Tripoli to tear down posters of the Libyan leader and cheer the news.
WATCH: Supporters celebrate as rebels advance into Tripoli:
Celebrations erupted elsewhere in Libya, including Benghazi, where tens of thousands turned out.
Speaking to journalists in London, Libyan charge d'affaires Mahmud Nacua claimed that the rebels now controlled 95 percent of Tripoli and the country.
Nacua repeated the rebel National Transitional Council's commitment to democracy and human rights.
"We look forward to build[ing] a democratic country," he said. "We will have [a] constitution. We will have freedom in every part of the country and different fields of activities."
The rebels told Western media that Saif al-Islam, a son of Qaddafi and onetime heir apparent, had been captured. The International Criminal Court later said it had received confirmation of his arrest.
Along with his father, Saif al-Islam has been charged by the ICC with crimes against humanity.
However, early on August 23, Saif al-Islam turned up at the Tripoli hotel housing many foreign journalists to prove he was, in fact, free. He said his father was safe and that Tripoli had not fallen to the rebels.
Another son, Mohammed, had confirmed to Al-Jazeera that the rebels had him under house arrest, but Al-Jazeera reported late on August 22 that he had escaped with the help of forces loyal to his father.
Loyalist fighters reportedly stormed the house where Mohammed was held and set him free after clashes with guards there.
Jalil, the opposition leader, told reporters that a third son, Al-Saadi, had also been detained.
South Africa, meanwhile, has denied speculation it had sent planes to Libya to allow Qaddafi to leave the country.
compiled from agency reports
Rebel fighters tear up a green Qaddafi-era flag in the rebels' headquarters at the former female military base in Tripoli on August 22.