Colonel Muammar Gaddafi's regime today announced an immediate ceasefire after David Cameron ordered RAF fighters to the Mediterranean to help enforce a military no-fly zone.
The Prime Minister said he was sending Typhoon and Tornado jets - as part of a joint operation with the US and France - in order to prevent a "bloodbath" in the rebel stronghold of Benghazi.
But shortly after he made the announcement in the House of Commons, the Libyan foreign minister declared that the regime accepted demands by the United Nations for a halt to the violence.
"Libya is a full member of the United Nations. We accept that it is obliged to accept the UN Security Council resolution," he told a news conference in Tripoli.
"Therefore Libya has decided an immediate ceasefire and the stoppage of all military operations."
The announcement will be treated with caution by Britain and its allies after they last night won backing for a resolution authorising "all measures necessary" short of a land invasion to protect the Libyan population.
"We will judge him by is actions, not his words," Mr Cameron told Channel 4 News during a round of broadcast interviews.
Earlier, the Prime Minister told the Commons that Libyan warplanes had already begun bombing Benghazi in preparation for an expected all out assault on the city by land, sea and air.
"The clock is now ticking. We need now a sense of urgency because we do not want to see a complete bloodbath in Benghazi and further repression and killing of civilian life in Libya," he said.
"Any decision to put the men and women of our armed forces into harm's way should only be taken when absolutely necessary.
"But I believe that we cannot stand back and let a dictator whose people have rejected him kill his people indiscriminately. To do so would send a chilling signal to others."
Mr Cameron said that preparations to deploy the RAF aircraft had already started and that they would begin heading out to bases in the region within hours.
In addition to the fast jet fighters, he said that surveillance and air-to-air refuelling aircraft were being sent.
There was no immediate announcement where they would be operating from, although there is speculation that they could use bases in Cyprus and Sicily.
Mr Cameron told MPs they would have a chance to vote on the decision to intervene in Libya in a Commons debate on Monday - although he could not afford to wait until then to act.
Following the Security Council vote in New York, the Prime Minister spoke to US President Barack Obama and French President Nicolas Sarkozy to discuss their next steps.
He will travel to Paris tomorrow for further talks with Mr Sarkozy and Arab League leaders who have thrown their weight behind calls for a military no-flight zone.
Mr Cameron said that a clear statement would be issued later today setting out exactly what Col Gaddafi has to do to comply with the Security Council resolution.
Earlier Mr Cameron chaired an emergency session of the Cabinet, attended by the Chief of the Defence Staff, General Sir David Richards.
The Attorney General Dominic Grieve briefed ministers on the legal position. A note summarising his advice will be published before the Commons debate on Monday.
Deputy Prime Minister Nick Clegg - who opposed the invasion of Iraq arguing that it was illegal - made clear that he was fully behind the intervention.
"This is not Iraq, we are not going to war, we are not invading Libya. What we are doing is upholding the international rule of law following the vote at the UN," the Liberal Democrat leader said.
Labour leader Ed Miliband also voiced his support saying that it would be "quite wrong" for Britain to "stand by and do nothing".
The news of the Security Council resolution was greeted with scenes of wild celebration last night on the streets of Benghazi.
But the immediate response of the regime was a familiar show of defiance. Gaddafi's son Saif said: "The resolution is unfair, because as you know from the beginning we have proved to everybody that there have been no air strikes against civilians."
In an interview broadcast shortly before the vote, Col Gaddafi said the UN had "no mandate" and added: "If the world is crazy, we will be crazy too."
The late-night vote at the Security Council in New York - by 10 to zero with five abstentions - came after days of stalling and intense telephone diplomacy by Mr Cameron with Arab, African and European leaders.
Impetus behind Resolution 1973, drafted by the UK, France and Lebanon, shifted with a U-turn on support for action by the United States - which went still further in backing air strikes.
Russian and Chinese concerns were overcome sufficiently to persuade them not to exercise their vetoes and they abstained - along with Germany, India and Brazil.
The resolution condemns Gaddafi's "gross and systematic violation of human rights" which "may amount to crimes against humanity" and pose a "threat to international peace and security".
It calls for "a complete end to violence and all attacks against, and abuses of, civilians" and authorises UN member states "to take all necessary measures (notwithstanding the previous arms embargo) to protect civilians and civilian populated areas under threat of attack".
It specifically excludes however "a foreign occupation force of any form on any part of Libyan territory".
The resolution also tightens previous sanctions including an arms embargo and an assets freeze and introduces measures to make it harder for Gaddafi to employ foreign mercenaries.
In a speech to the Scottish Conservative conference in Perth, Mr Cameron pledged that he would not allow Britain's armed forces to shoulder too large a share of the burden over Libya.
Britain's involvement was not "the start of some ideologically-driven mission, without limit, in which we set out to cure all the world's ills", he promised.
"The UN resolution confers a duty on Britain, along with the other permanent members of the Security Council who supported it, to play our part in implementing it," said Mr Cameron.
"With the fourth largest military in the world, Britain has the means to play that part.
"But given that British troops are currently engaged in Afghanistan, that part must be in line with our resources. And so it will be."
Britain will be working alongside a number of Arab countries in implementing the resolution and will do "our fair share - no more, no less", he said.
And he added: "We should never contemplate military force without thinking carefully of the people we ask to go into action, and their families and loved ones too.
"Our Army, Navy and Air Force are the best of our nation. The bravest of the brave... We must never ask you to act without thinking of the consequences.
"But I believe this course is good and just and right."
Mr Cameron said Britain was committing itself to military action "at a level that matches our resources, in alliance with other countries, with the full authority of the United Nations Security Council and in accordance with international law".
And he added: "This is why we are acting, not just the moral duty to step in when a dictator starts killing his own people, not just the belief that a movement towards more open and democratic government in the Arab world will be good for the entire world.
"But the clear and hard-headed understanding that a stable Libya, free from Colonel Gaddafi's brutality, is in Britain's long-term interests too.
"This is where our ideals and our interests come together.
"And I know that the British people, as they always do in times of crisis, will unite behind the action we are taking in the cause of justice and freedom for the safety of our nation and the security of our world."Reuse content