Western powers launched a second wave of air strikes on Libya early on Monday after halting the advance of Muammar Gaddafi's forces on Benghazi and targeting air defences to let their planes patrol the skies.
But the United States, carrying out the air strikes in a coalition with Britain, France, Italy and Canada among others, said the campaign was working and dismissed a ceasefire announcement by the Libyan military on Sunday evening.
Britain's Defence Ministry said one of its submarines had again fired Tomahawk guided missiles on Sunday night as part of a second wave of attacks to enforce the U.N. resolution.
"We and our international partners are continuing operations in support of the United Nations Security Council Resolution 1973," a ministry spokesman said.
Italy said it also had warplanes in the air, after U.S. and British warships and submarines launched 110 Tomahawk missiles on Saturday night and Sunday morning.
Vice Admiral Bill Gortney, director of the U.S. military's Joint Staff, told reporters there had been no new Libyan air activity or radar emissions, but a significant decrease in Libyan air surveillance, since strikes began Saturday.
Benghazi was not yet free from threat, said Gortney, but Gaddafi's forces in the area were in distress and "suffering from isolation and confusion" after the air assaults.
Late on Sunday night, Libyan officials took Western reporters to Gaddafi's compound in Tripoli, a sprawling complex that houses his private quarters as well as military barracks, anti-aircraft batteries and other installations, to see what they said was the site of a missile attack two hours earlier.
"It was a barbaric bombing," said government spokesman Mussa Ibrahim, showing pieces of shrapnel that he said came from the missile. "This contradicts American and Western (statements) ... that it is not their target to attack this place."
A Libyan military spokesman announced a new ceasefire on Sunday, saying that "the Libyan armed forces ... have issued a command to all military units to safeguard an immediate ceasefire from 9 p.m. (1900 GMT) this evening".
Both before and after he spoke, heavy anti-aircraft gunfire boomed above central Tripoli.
Outside Benghazi, smouldering, shattered tanks and troop carriers from what had been Gaddafi's advancing forces littered the main road. The charred bodies of at least 14 government soldiers lay scattered in the desert.
But with Gaddafi having vowed to fight to the death, there were fears his troops might try to force their way into cities, seeking shelter from air attacks among the civilian population.
In central Benghazi, sporadic explosions and heavy exchanges of gunfire could be heard in the streets late on Sunday evening. A Reuters witness said the firing lasted about 40 minutes.
In Misrata, the last rebel-held city in western Libya, government tanks moved in after a base used by Gaddafi's forces outside was hit by air strikes on Saturday, residents said.
"There is fighting between the rebels and Gaddafi's forces. Their tanks are in the centre of Misrata ... There are so many casualties we cannot count them," Abdelbasset, a spokesman for the rebels in Misrata, told Reuters on Sunday afternoon.
A Libyan government health official said 64 people had been killed by Western bombardment on Saturday and Sunday morning, but it was impossible to independently verify the report.
Libyan state television showed footage from an unidentified hospital of what it called victims of the "colonial enemy". Ten bodies were wrapped in white and blue bed sheets, and several people were wounded, one of them badly, the television said.
Arab League Secretary-General Amr Moussa called for an emergency meeting of the group's 22 states to discuss Libya. He requested a report on the bombardment, which he said had "led to the deaths and injuries of many Libyan civilians".
"What is happening in Libya differs from the aim of imposing a no-fly zone, and what we want is the protection of civilians and not the bombardment of more civilians," Egypt's state news agency quoted him as saying.
There was no immediate public backing for his call from any government in the region, however.
Arab support for a no-fly zone provided crucial underpinning for the passage of a U.N. Security Council resolution last week that paved the way for Western action to stop Gaddafi killing civilians as he fights an uprising against his 41-year rule.
U.S. President Barack Obama spoke to Jordan's King Abdullah, while Vice President Joe Biden phoned leaders in Algeria and Kuwait to shore up Arab support.
The intervention is the biggest against an Arab country since the 2003 invasion of Iraq. Withdrawal of Arab support would make it much harder to pursue what some defence analysts say could in any case be a difficult, open-ended campaign with an uncertain outcome.
A spokesman for the rebel movement, Abdel Hafiz Ghoga, criticised Moussa's comments, telling Al Jazeera that more than 8,000 Libyans aligned with the rebel movement had been killed:
"What is the mechanism that stops the extermination of the people in Libya, what is the mechanism, Mr Secretary-General? If the protection of civilians is not a humanitarian obligation, what is the mechanism that you propose to us?"
The U.S. Chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, said the no-fly zone was now in place.
But Defense Secretary Robert Gates said the U.S. would not have a "pre-eminent role" in maintaining it, and expected to turn over "primary responsibility" within days, perhaps to Britain or France.
U.S. officials, eager to avoid similarities to the invasion of Iraq and toppling of Saddam Hussein, have been playing down Washington's role and emphasising that overthrowing or killing Gaddafi is not the goal of the attacks on Libya.
Mullen told CBS television the endgame of the campaign was "very uncertain" and acknowledged it could end in a stalemate.
Gates told reporters: "I think this is basically going to have to be resolved by the Libyans themselves."
In Brussels, NATO envoys failed to agree on any alliance involvement in enforcing the no-fly zone.
NATO members Turkey and Germany have spoken out against the zone, and diplomats said France had argued against involvement by an alliance whose reputation in the Arab world had been tainted by its involvement in the war in Afghanistan.
French planes fired the first shots of the intervention on Saturday, destroying tanks and armoured vehicles near Benghazi.
France sent an aircraft carrier towards Libya and its planes were over the country again on Sunday, defence officials said. Britain said its planes had targeted Libya's air defences, mainly around the capital Tripoli.
Other countries, including Qatar, also dispatched aircraft to participate in the operation, U.S. officials said.