MPs have voted overwhelmingly to support UN-backed action in Libya, after David Cameron told them it had helped avert a "bloody massacre".But the prime minister assured the House of Commons that Libya would not become "another Iraq", amid concerns raised about long-term plans.
The government motion, also backed by Labour, won a majority of 544.
The debate focused on Resolution 1973, passed by the United Nations Security Council last week. This authorises "all necessary measures", short of bringing in an occupying force, to protect Libyan citizens from the Gaddafi regime, which has been fighting rebel forces.
The Commons motion - which was backed by 557 MPs and opposed by 13 - followed a second night of US-led action in Libya, with Col Gaddafi's sprawling Bab al-Aziziya complex in Tripoli among the locations hit.
Fighting continues, with anti-aircraft fire heard in Tripoli late on Monday.
'Nick of time'
During the debate Mr Cameron said a no-fly zone had "effectively been put in place over Libya".
While most MPs expressed their support for the action, 13 MPs and two "tellers" voted against the motion - including 11 Labour MPs, one Conservative, the Green's sole MP and two members of the SDLP. Twenty five Conservatives, 32 Labour MPs, five DUP, one SDLP and one independent MP did not vote. either because they wanted to abstain or because they were not available.Some questions were raised about its scope and post-conflict planning.
SNP Westminster leader Angus Robertson asked about the "potential for mission creep", with Mr Cameron replying that the UN resolution was about protecting civilians: "I've been clear. I think Libya needs to get rid of Gaddafi. But in the end we are responsible for trying to enforce this Security Council resolution. The Libyans must choose their own future."
Defence Secretary Liam Fox has suggested targeting the Libyan leader could "potentially be a possibility" for UN coalition forces, but the head of the UK armed forces, General Sir David Richards, said on Monday that Col Gaddafi was "absolutely not" a target under the terms of the UN resolution.
Mr Cameron appeared to back Gen Richards, saying that "the UN resolution is limited in its scope. It explicitly does not provide legal authority for action to bring about Gaddafi's removal from power by military means."
Labour veteran MP Dennis Skinner told the prime minister: "It is easy to get into a war; it is harder to end it. When will we know what the circumstances are for pulling out and ending the war?"
Mr Cameron replied: "This is different to Iraq. This is not going into a country, knocking over its government and then owning and being responsible for everything that happens subsequently. This is about protecting people and giving the Libyan people a chance to shape their own destiny."
Several MPs questioned why action was being taken in Libya, but not in Yemen or Bahrain, which have also been using violence to crack down on protests.
Labour leader Ed Miliband said he supported the action, arguing it was "a just cause, with a feasible mission, and it has international support".
"We have seen with our own eyes what the Libya regime is capable of," he said.
"We have seen guns being used on unarmed demonstrators. We have watched warplanes and artillery being used against civilian population centres. We have learned of militia violence and disappearances in areas held by Gaddafi forces."
But Labour MP David Winnick, who was not expected to support the motion, said: "Many innocent people are going to be killed or slaughtered - whatever word you're are going to use - because it can't otherwise be the situation."
Ahead of the debate, the government published a note saying action was legal.
It set out the basis for UN Resolution 1973, finding the UN Security Council had "determined that the situation in the Libyan Arab Jamahiriya constitutes a threat to international peace and security" and aimed to restore it under Chapter Seven of the UN Charter.
The parliamentary motion, tabled by the government, asked MPs to support action "in accordance" with the resolution and to "acknowledge the demonstrable need, regional support and clear legal basis for urgent action to protect the people of Libya".
The UK government does not require Parliament's approval to deploy troops. However, in practice, governments have involved MPs by scheduling debates, statements and - as with the 2003 Iraq invasion - sometimes substantive votes on proposals to do so.