The two eldest sons of former Libyan leader Muammar Gaddafi are in rebel custody, but the whereabouts of other relatives and senior officials remain unknown.
Gaddafi's second-eldest son, Saif al-Islam, was detained by rebels on Sunday night, according to Mustafa Abdul Jalil, the head of the rebel National Transitional Council (NTC). The council provided few other details.
Hours later, a spokesman for the International Criminal Court (ICC) confirmed the arrest. The opposition has not announced whether it will hand over prisoners to the ICC.
The ICC issued an arrest warrant for Saif al-Islam in June on charges of crimes against humanity. Luis Moreno-Ocampo, the court's chief prosecutor, described Saif al-Islam as Libya's "de facto prime minister", and accused him of recruiting foreign mercenaries that reportedly attacked protesters during Libya's six-month uprising.
"We hope he can soon be in The Hague," Moreno-Ocampo said on Monday.
Still, the rebels have not yet said whether they will transfer Saif al-Islam to the ICC. Representatives from the court and the rebel council are scheduled to meet on Monday to discuss a possible transfer.
Libya uprising timeline
17 Feb: Anti-government protests begin across Libya
24 Feb - 6 Mar: Rebels seize control of several towns and cities but are driven back
17 Mar: UN authorises no-fly zone and "all necessary measures" to protect civilians
19 Mar: First strikes by US, French and British warplanes halt pro-Gaddafi forces
30 Mar: Foreign Minister Moussa Koussa defects
16-25 Apr: Gaddafi forces bombard rebel-held Misrata
May-Jul: Stalemate as rebels and government troops engage in skirmishes
Mid-Aug: Rebels seize key towns of Zawiya and Gharyan outside Tripoli
21 Aug: Rebels enter Tripoli
Libyan communities around the world come out in force to sing and chant, anticipating an end to Muammar Gaddafi's rule.
Celebrations have spilled over from Tripoli and Benghazi into cities around the world, as the Libyan diaspora gathered to celebrate the advance of opposition forces.
At least a hundred Libyans gathered outside the White House on Monday to celebrate the rebel's assault on Tripoli, waving the country's flag and chanting "Libya is free" and "Thank you, Obama".
"Tonight for the first time in our lives we are very proud to be Libyan," Rania Swadek, a 33-year-old Libyan-American, told the AFP news service. Swadek was waving a sign showing the red, black and green rebel flag with the words "Thank you, NATO! Thank you, Obama!"
The mother of two, who arrived in the US in 1984 with her brothers and sisters after receiving political asylum, also had kind words for France, which was among the first countries to call for international intervention in Libya.
"We want to say thank you to President Nicolas Sarkozy and the French people who were the first, even before the Americans, to support the Libyans in their struggle," she said.
While Gaddafi's regime has not yet fallen, many Libyans were celebrating what they believed was the beginning of the end.
"They already have the sons," Swadek said, referring to reports that one of Gaddafi's sons, Saif al-Islam, had been arrested and another, Mohammad Gaddafi, also detained by rebels.
"Now we want him alive for a trial for all the crimes against humanity he has done, not just now but for four decades," Swadek said, referring to Gaddafi.
'Replace the flag'
Libyans gathered outside their embassy in Cairo on Monday and demanded that the green flag of Gaddafi be replaced with the opposition's flag.
"As an individual, my demands would be first and foremost, since I'm here in Cairo, for the Libyan embassy in Cairo to lower its flag and raise the flag of the independence and for the Egyptian military council to recognise the [National] Transitional Council," said Omar, a Libyan celebrating in Cairo, who did not disclose his last name.
Dressed in white T-shirts and waving Libyan independence flags, the jubilant crowd shouted, "Replace the flag! Replace the flag!"
In Alexandria, Egypt, hundreds gathered outside the consulate and also clamoured for the removal of the green flag of Gaddafi.
Crowds also gathered outside the Libyan embassy in Tunis, capital of Tunisia, celebrating the reports of the fighting in Tripoli. Waving the flag of independence, many expressed their joy at the news.
The Libyan ambassador in Malta allowed the removal of the Gaddafi flag and raised the emblem of the opposition forces. About 100 people gathered to celebrate the battle for Tripoli.
According to Malta Today, pro-rebel supporters chanted "Libya, Libya", and "Down with Gaddafi". Authorities allowed demonstrators to enter the embassy where they took to the roof and replaced the old flag.
In Sarajevo, however, police were forced to surround the embassy after a dozen Libyans entered the building, threw Gaddafi's pictures out the windows, raised the rebels' flag, and demanded the resignation of the ambassador.
Yet, according to an embassy employee who spoke to The Associated Press, the ambassador is a 'die-hard Gaddafi supporter' who refuses to leave. Currently the Bosnian police are inside the building trying to keep the negotiations peaceful.
Wait is 'finally' over
In Washington, children wore "Free Libya" shirts with the colors of the rebel flag. One demonstrator waved a large multicoloured sign with the capital letters "FINALLY".
Libyans sang in English: "Gaddafi left Tripoli, Libya is free".
About 40 men knelt facing Mecca to pray, some used the rebel flag as a prayer mat.
Among them was Khaled Rouini, a 42-year-old Tunisian taxi driver, who could not hide his excitement.
"I came to the White House to celebrate the revolutions in Tunisia and Egypt," he said, sporting a "Free Libya" T-shirt. "And now it is in Libya," he added.
Ahmed Ilhnish, draped in the rebel flag, said he had been overwhelmed by emotions.
"There is no word to tell what we feel," he said. "Now it is just a matter of time."
"I have been waiting this day since the day I was born," Ilhnish continued. "I was in Benghazi in March when the French planes first came. I'm going to get back in Tripoli tomorrow or in a few days as soon as they get him."