The U.N. Security Council voted to impose a no-fly zone over Libya and authorized "all necessary measures" to prevent Moammar Gadhafi's planes from carrying out aerial attacks on rebel-held positions.
The vote late Thursday was 10-0 with five abstentions, including Russia and China.
The United States, France and Britain pushed for speedy approval because Gadhafi's forces are advancing toward opposition-held Benghazi. The Libyan leader vowed Thursday night to oust the rebels from their eastern stronghold.
The resolution, drafted by France, Britain and Lebanon, authorizes U.N. member states "to take all necessary measures ... to protect civilians and civilian populated areas under threat of attack ... including Benghazi, while excluding an occupation force."
French Prime Minister Francois Fillon said if the resolution was approved, France would support military action against Gadhafi within hours. The U.S. said it was preparing for action.
The vote came after closed-door consultations Thursday afternoon on the text of the resolution, which was sent to capitals of the 15 council nations overnight for comments.
The resolution calls for stronger enforcement of the arms embargo; adds names of individuals, companies and other entities to the list of those subject to travel bans and asset freezes; and requires all countries to ban Libyan flights from landing, taking off or flying over their country.
It demands that Libya ensure the "rapid and unimpeded" passage of humanitarian assistance.
Earlier U.S. Secretary of State Hillary Clinton, who was in Tunisia to meet with the country's new leaders and discuss possible U.S. assistance, said a U.N. no-fly zone over Libya would require the bombing of targets to take out the threat posed by Gadhafi's regime.
Libya's defense minister had threatened that any Western airstrikes would endanger air and sea traffic in the Mediterranean now and in the future.
Gadhafi's rapid eastward advance on rebel-held positions appears to have spurred the United States to leave behind weeks of doubts about a no-fly zone in Libya and push for broader U.N. authorization for international air, sea and land forces.
Libya's opposition movement had hoped the Security Council would act to help keep Gadhafi's forces from retaking the city of Ajdabiya, the last major city between government troops and the rebel stronghold of Benghazi.
Mustafa Gheriani, a spokesman for the opposition in Benghazi, said by telephone earlier Thursday that if a U.N. resolution failed to pass, "we'll rely on ourselves and do what we can."
"Short of the genocide of east Libya there's little Gadhafi can do because he can't rule us anymore," Gheriani said.
Loyalists had surrounded Adjabiya on three sides by Thursday afternoon, fending off rebel airstrikes about 10 miles from the city's western gate, activist Abdel-Bari Zwei told the AP.
Charred vehicles, bullet-riddled pickup trucks and an overturned tank littered the desert highway where pro-Gadhafi forces had fought up to the entrance of Ajdabiya, a city of 140,000. An Associated Press Television News cameraman counted at least three bodies by the side of the road, evidence of fierce battles. Regime troops were bringing in a stream of truckloads of ammunition, rockets and supplies.
Gadhafi's army also reportedly seized the nearby port town of Zwitina to the north.
But the rebels scored a rare success in the struggle against Gadhafi's superior air power — shooting down at least two bomber planes that attacked the airport in Benghazi, according to AP reports citing accounts from residents.
Gheriani said opposition fighters used three of their own seized planes and some helicopters to attack government troops trying to advance on Benghazi.
The government has won a string of victories in eastern Libya, and the decisive battleground may now be Benghazi, the country's second-largest city and the heart of the revolution.
NPR's David Greene reported that the regime has passed out leaflets to residents urging support for Gadhafi and dangled promises of amnesty for those who put down their arms. But there's still a sense of fear across Libya that those who joined in the protests may never be safe.
The New York Times said four of its journalists disappeared Tuesday while reporting on the fighting in Ajdabiya, and the aid group Doctors Without Borders pulled its staff out of Libya owing to security concerns.
A Benghazi resident who did not want to be identified for fear of reprisals said the city's young men were volunteering to undergo basic military training. Those already trained were seeking more preparation to be battle ready.
More checkpoints were popping up at intersections and on main roads, manned by men in uniform armed with AK-47s and backed by anti-aircraft guns mounted on pickup trucks.
A rebel spokesman told the AP that Benghazi was "armed to the teeth" and the opposition is ready to defend it. Opposition fighters claimed to have gained control of an oil tanker Wednesday and rerouted it from Tripoli to Benghazi.
But Greene said that Gadhafi's better-trained military has proved largely unstoppable, which has made rebel calls for international help even louder.
