The UN Security Council has approved a no-fly zone over Libya and authorised "all necessary measures" to protect civilians from attacks by Moammar Gaddafi's forces.
The vote tonight was 10-0 with five abstentions, including Russia and China.
The United States, France and Britain pushed for speedy approval because Gaddafi's forces are advancing toward opposition-held Benghazi.
The Libyan leader vowed tonight to oust the rebels from their eastern stronghold.
French Prime Minister Francois Fillon said if the resolution was approved, France would support military action against Gaddafi within hours. The US said it was preparing for action.
Foreign Secretary William Hague said the UN resolution was necessary "to avoid greater bloodshed and to try to stop what is happening in terms of attacks on civilians".
The UK's three criteria for a no-fly zone - a demonstrable need, a clear legal basis and broad regional support - were now all met, he said.
"This places a responsibility on members of the United Nations and that is a responsibility to which the United Kingdom will now respond".
The resolution also tightened sanctions and introduced measures to make it harder for Gaddafi to employ foreign mercenaries.Reuse content