Following a day and a night of dramatic developments in Libya, as rebels opposed to Muammar Gaddafi took control of most parts of Tripoli, here is how world leaders and institutions reacted to the crumbling of the Gaddafi regime:

United States 

President Barack Obama said the situation in Libya had reached a "tipping point" and that control of the capital was "slipping from the grasp of a tyrant." He called on Muammar Gaddafi to accept reality and relinquish power.

“The surest way for the bloodshed to end is simple: Muammar Gaddafi and his regime need to recognize that their rule has come to an end," Obama said in a statement issued during his vacation in Martha's Vineyard. "Gaddafi needs to acknowledge the reality that he no longer controls Libya. He needs to relinquish power once and for all." 

United Kingdom 

Deputy Prime Minister Nick Clegg will declare on Monday that Britain will not "turn its back" on the millions of people in the Arab world fighting for their freedom.

In a speech on the "Arab spring" to a British Council event in London, the deputy prime minister is expected to say that British intervention in Libya has already saved "tens, if not hundreds, of thousands of lives" and that, although it is not certain exactly how events in the region will develop, the overall "direction of travel" is clear.

"The fundamental forces driving these changes are here to stay," he will say. "Youth. Technology. A lack of opportunity and inclusion. Factors which have collided to create citizens who want more, who know more, who aspire to more. But who are denied it at every turn.

"This year that tension has hit boiling point. We can be confident the appetite for reform will remain." Clegg will say that Britain "will not turn its back on the millions of citizens of Arab states looking to open up their societies, looking for a better life."

Preparations for a "strong, stable, post-Gaddafi Libya" are already underway, he will say. "We are determined to learn the lesson of Iraq: no matter where you are in the conflict, you should already be planning for the peace." 

International Criminal Court (ICC)

The International Criminal Court and Libyan rebels are to hold talks Monday on transferring a captured son of Gaddafi who is wanted on charges of crimes against humanity, the court's chief prosecutor told CNN. Luis Moreno-Ocampo confirmed Sunday that Saif Al Islam had been arrested as rebels advanced and entered Tripoli over the weekend.

Gaddafi, Al Islam and Abdullah Al Sanussi, Gaddafi's brother-in-law and Libya's intelligence chief, are all wanted by The Hague-based court in connection with efforts by Gaddafi's government to put down the revolt against his rule, which began in February.

Moreno-Ocampo told CNN the arrest warrants must be enforced. He said he did not know the whereabouts of al-Islam because the court had yet to have contact with the rebel Transitional National Council. His arrest was confirmed by other sources, the Argentine prosecutor said. "We'll discuss tomorrow the transition of authority, how to manage to surrender him," Moreno-Ocampo said. Gaddafi's and Al Sanussi's whereabouts were not known, but Gaddafi's eldest son, Mohammad Gaddafi, was also reportedly arrested Sunday. 

Australia

Australian Prime Minister Julia Gillard has called on Gaddafi to get out of his people's way and to face charges for alleged crimes against them. Australia was among the first countries to call for the United Nations to enforce a no-fly zone over Libya as Gaddafi's forces violently suppressed rebellion among his people.

She said Australia will support the country toward peace and democracy. She said: "We continue to call on Colonel Gaddafi to get out of the way and of course we believe he should face the international charges that are against him." 

Denmark

Libya's conflict between rebel fighters and backers of Muammar Gaddafi has entered its "end game," Danish Prime Minister Lars Loekke Rasmussen said. "It's absolutely critical that the final phase is handled in a dignified manner and that the National Transitional Council is united in steering the transition toward free elections," Rasmussen said in a statement published on his office's website today.