Shelling has been heard on the outskirts of a rebel-held city in eastern Libya and a fighter jet was seen overhead.
Two columns of smoke were rising just outside Benghazi on Saturday. Further details were not immediately available.
Moammar Gadhafi's government declared a cease-fire against the rebel uprising Friday in an attempt to outmaneuver Western military intervention. But the opposition has been saying shells rained down well after the announcement and accused the Libyan leader of lying.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
TRIPOLI, Libya (AP) — Trying to outmaneuver Western military intervention, Moammar Gadhafi's government declared a cease-fire against the rebel uprising faltering against his artillery, tanks and warplanes. The opposition said shells rained down well after the announcement and accused the Libyan leader of lying.
Wary of the cease-fire, Britain and France took the lead in plans to enforce a no-fly zone, sending British warplanes to the Mediterranean and announcing a Saturday crisis summit in Paris with the U.N. and Arab allies. In Washington, President Barack Obama ruled out the use of American ground troops but warned that the U.S., which has an array of naval and air forces in the region, would join in military action.
There should be no doubt about the Libyan leader's intentions "because he has made them clear," Obama said. "Just yesterday, speaking of the city of Benghazi, a city of roughly 700,000, he threatened 'we will have no mercy and no pity.' No mercy on his own citizens."
In a joint statement to Gadhafi late Friday, the United States, Britain and France — backed by unspecified Arab countries — said a cease-fire must begin "immediately" in Libya, the French presidential palace said.
The statement called on Gadhafi to end his troops' advance toward Benghazi, the rebel headquarters, and pull them out of the cities of Misrata, Ajdabiya and Zawiya, and called for the restoration of water, electricity and gas services in all areas. It said Libyans must be able to receive humanitarian aid or the "international community will make him suffer the consequences" with military action.
Parts of eastern Libya, where the once-confident rebels this week found their hold slipping, erupted into celebration at the passage of the U.N. resolution. But the timing and consequences of any international military action remained unclear.
Britain, France and NATO held emergency meetings Friday on using military force to enforce the no-fly zone, which was approved by U.N. Security Council on Thursday. Officials announced that the leaders of Britain, France and Germany and the chiefs of the United Nations and Arab League would join other world leaders for an emergency summit on Libya in Paris Saturday.
France's ambassador to the United Nations, Gerard Araud, told BBC Newsnight that he expected military action to begin in Libya within hours of the Paris meeting.
Misrata, Libya's third-largest city and the last held by rebels in the west, came under sustained assault well after the cease-fire announcement, according to rebels and a doctor there. The doctor, who spoke on condition of anonymity because he feared reprisals, said Gadhafi's snipers were on rooftops and his forces were searching homes for rebels.
"The shelling is continuing, and they are using flashlights to perform surgery. We don't have anesthetic to put our patients down," said the doctor, who counted 25 deaths since the morning.
Libya's deputy foreign minister, Khaled Kaim, denied government forces had violated the cease-fire and invited four nations to send observers to monitor compliance: Germany, China, Turkey and Malta.
"The cease-fire for us means no military operations whatsoever, big or small," he told reporters in Tripoli.
He said military forces were positioned outside Benghazi but that the government had no intention of sending them into the city.
He also invited the U.N. chief to send a fact-finding mission and asserted that the rebels had committed crimes against humanity.
But Susan Rice, the U.S. ambassador to the United Nations, said Gadhafi is violating the U.N. resolution. She told CNN the resolution demanded an immediate cease-fire and end to all offensive operations
"The U.S. is ready to act, along with partners from the League of Arab States and Europe," she said. "Gadhafi should be under no illusions that if he doesn't act immediately he'll face swift and sure consequences, including military action."
The rebels still hold eastern Libya, which has most of the country's oil reserves. Oil prices slid after the cease-fire announcement, plunging about $2.50 in the first 15 minutes of New York trading. They were down slightly for the week, settling at $101.07 per barrel on the New York Mercantile Exchange.
Mustafa Gheriani, a spokesman for the rebels, said the opposition is considering calling Gadhafi's bluff by holding new protests in Tripoli and elsewhere in Gadhafi's western strongholds to see if his forces open fire.
"The idea is that when he cannot bomb civilians, the whole world will see that Libya does not want him," Gheriani said. "I believe his troops in Tripoli will leave him. We want to make our revolution a peaceful one again, just surround his compound and make him leave."
Gheriani and Khaled Sayh, another rebel spokesman, said shelling continued late Friday in Zintan, a western mountain town; Misrata and Ajdabiya, an eastern city that has been surrounded by government forces.
But even in advanced militaries, orders can take time to make it through the ranks, and it wasn't clear if all of Gadhafi's front-line troops had received the cease-fire directive by late Friday.
In Washington, Secretary of State Hillary Rodham Clinton said the immediate objective of any intervention was to halt violence against civilians, but insisted that the "final result of any negotiation would have to be the decision by Col. Gadhafi to leave."
The U.N. Security Council resolution set the stage for airstrikes, a no-fly zone and other military measures short of a ground invasion. Within 12 hours, Gadhafi's government announced "an immediate cease-fire and to stop all military operations," said Libyan Foreign Minister Moussa Koussa.
The U.S. was proceeding cautiously in the face of Libya's announcement, as Obama attempted to navigate between exercising too much U.S. military power and doing too little to help rebels seeking Gadhafi's ouster.
"The driving consideration is what comes next if a no-fly zone doesn't work," said Aaron David Miller, a former Mideast adviser to six U.S. secretaries of state.
"I think Gadhafi's capacity to survive has little or nothing to do with us. If anything, we've lent to his bizarre system of government through the way we've demonized him in the past. To some degree, we've played into his hands," said Miller, now with the Woodrow Wilson Center think tank.
After the resolution passed, a crowd watching the vote on an outdoor TV projection in Benghazi — the first city swept up in the uprising that began Feb. 15 — burst into cheers, with green and red fireworks exploding overhead. In Tobruk, another eastern city, happy Libyans fired weapons in the air to celebrate.
"We think Gadhafi's forces will not advance against us. Our morale is very high now. I think we have the upper hand," said Col. Salah Osman, a former army officer who defected to the rebel side. He was at a checkpoint near the eastern town of Sultan.
Western powers faced pressure to act quickly as Gadhafi's forces gained momentum.
"We're extremely worried about reprisals by pro-government forces and security agents in Libya. No one knows what's going on in the towns recaptured, and what's going on in prisons and other state security premises across the country," said Rupert Colville, spokesman for the U.N. Office of the High Commissioner for Human Rights. "We are very concerned that the government could resort to collective punishment and we have no illusions about what this regime is capable of."
More than 300,000 people have fled Libya since fighting began, the U.N. said Friday, and the exodus shows no signs of slowing. The U.N. said between 1,500 and 2,400 people have been crossing the borders with Egypt and Tunisia each day.
Melissa Fleming, the spokeswoman for the U.N. refugee agency, said officials were working with Egypt — which borders eastern Libya — to prepare for a potentially "massive influx of people fleeing the violence in Libya."
"It is also possible that the current conflict could cut off access to safe places and passage out of the country," she said.
Lucas reported from Benghazi, Libya. Associated Press writers Slobodan Lekic in Brussels; Jill Lawless in London; and Jamey Keaten in Paris contributed to this report.