The U.S. military said the bombardment so far - a rain of Tomahawk cruise missiles and precision bombs from American and European aircraft, including long-range stealth B-2 bombers - had succeeded in heavily degrading Gadhafi's air defenses.
But the international campaign went beyond hitting anti-aircaft sites. U.S., British and French planes blasted a line of tanks that had been moving on the rebel capital Benghazi, in the opposition-held eastern half of the country. On Sunday, at least seven demolished tanks smoldered in a field 12 miles (20 kilometers) south of Benghazi, many of them with their turrets and treads blown off, alongside charred armored personnel carriers, jeeps and SUVs of the kind used by Gadhafi fighters.
"I feel like in two days max we will destroy Gadhafi," said Ezzeldin Helwani, 35, a rebel standing next to the smoldering wreckage of an armored personnel carrier, the air thick with smoke and the pungent smell of burning rubber. In a grisly sort of battle trophy, celebrating fighters hung a severed goat's head with a cigarette in its mouth from the turret of one of the gutted tanks.
The strikes that began early Sunday gave immediate, if temporary, relief to Benghazi, which the day before had been under a heavy attack that killed at least 120 people. The city's calm on Sunday highlighted the dramatic turnaround that the allied strikes bring to Libya's month-old upheaval: For the past 10 days, Gadhafi's forces had been on a triumphant offensive against the rebel-held east, driving opposition fighters back with the overwhelming firepower of tanks, artillery, warplanes and warships.
Now Gadhafi's forces are potential targets for U.S. and European strikes. The U.N. resolution authorizing international military action in Libya not only sets up a no-fly zone but allows "all necessary measures" to prevent attacks on civilians.
But the U.S. military, for the time being at the lead of the international campaign, is trying to walk a fine line over the end game of the assault. It is avoiding for now any appearance that it aims to take out Gadhafi or help the rebels oust him, instead limiting its stated goals to protecting civilians.
At the Pentagon, Navy Vice Adm. William E. Gortney underlined that strikes are not specifically targeting the Libyan leader or his residence in Tripoli. He said that any of Gadhafi's ground forces advancing on the rebels were open targets.
"If they are moving on opposition forces ... yes, we will take them under attack," he told reporters.
"We judge these strikes to have been very effective in significantly degrading the regime's air defense capability," Gortney said. "We believe his forces are under significant stress and suffering from both isolation and a good deal of confusion." What happens if rebel forces eventually go on the offensive against Gadhafi's troops remains unclear. Gortney would not say whether strikes would hit Libyan troops fighting back against rebel assaults.
Sunday night, heavy anti-aircraft fire erupted repeatedly in the capital, Tripoli, with arcs of red tracer bullets and exploding shells in the dark sky - marking the start of a second night of international strikes. Gadhafi supporters in the streets shot automatic weapons in the air in a show of defiance. It was not immediately known what was being targeted in the new strikes.
Gadhafi vowed to fight on. In a phone call to Libyan state television Sunday, he said he would not let up on Benghazi and said the government had opened up weapons depots to all Libyans, who were now armed with "automatic weapons, mortars and bombs." State television said Gadhafi's supporters were converging on airports as human shields.
"We promise you a long war," he said.
He called the international assault "simply a colonial crusader aggression that may ignite another large-scale crusader war." Throughout the day Sunday, Libyan TV showed a stream of what it said were popular demonstrations in support of Gadhafi in Tripoli and other towns and cities. It showed cars with horns blaring, women ululating, young men waving green flags and holding up pictures of the Libyan leader. Women and children chanted, "God, Muammar and Libya, that's it!"
"Our blood is green, not red," one unidentified woman told the broadcaster, referring to the signature color of Gadhafi's regime. "He is our father, we will be with him to the last drop of blood. Our blood is green with our love for him."
Among the targets hit in the first night of strikes before dawn Sunday was one of Libya's main air bases, on Tripoli's outskirts, the opposition said. Also hit, it said, was an air force complex outside Misrata, the last rebel-held city in western Libya - which has been under siege the past week by Gadhafi forces. Those forces have been bombarding the city from the complex, which houses an air base and a military academy.
Despite the strikes, the troops resumed bombarding Misrata during the day Sunday, said Switzerland-based Libyan activist Fathi al-Warfali.
"Misrata is the only city in western Libya not under Gadhafi's control; he is trying hard to change its position," said al-Warfali, who told The Associated Press he was in touch with residents in the city.
On state TV, the Libyan armed forces repeated its claim that it ordered a cease-fire - though its units continued fighting after a similar cease-fire call the night before.
In Benghazi, the rebel capital and first city to fall to the uprising that began Feb. 15, residents were celebrating the dramatic turn of events. The day before, Gadhafi's forces pounded the city of around 700,000 with artillery and tank shells and punched through the outskirts in heavy street battles. Along the tree-lined road into Benghazi, buildings riddled with pockmarks and burnt-out cars, buses and tanks gave testimony to the ferocity of the fighting.
"Yesterday was a catastrophe," said Salwa el-Daghili, a member of the opposition national council that governs rebel-held territory. "Today, there is hope - you can see it on the streets."
Outside the city, hundreds of men roamed the wreckage of the tanks and army vehicles hit by the allied strikes. Shredded blankets, torn foam mattresses and empty cans of tomato paste littered the field.
"Thank you, France. Thank you, America," said Abdul-Gader Dejuli as he surveyed the wreckage. "Obama good, Sarkozy good."
The allied assault began in the early hours Sunday with a wave of strikes by French warplanes in the east, followed by a barrage of 112 cruise missiles fired by U.S. and British warships and submarines in the Mediterranean targeting radar systems,
communications centers and surface-to-air missile sites. Bombings mainly from American aircraft - including B-2 stealth bombers and F-15 and F-16 fighter-bombers - then targeted Libyan ground forces and air defenses, the U.S. military said.
The systems targeted most closely were Libya's SA-5 surface-to-air missiles, Russian-made weaponry that could pose a threat to allied aircraft many miles off the Libyan coastline. Libya has a range of other air defense weaponry, including portable surface-to-air missiles that are more difficult to eliminate by bombing.
Libya said 48 people were killed, including many civilians. That brought criticism of the campaign from the head of the Arab League, which last week took the unprecedented step of calling for a no-fly zone. On Sunday, Arab League chief Amr Moussa criticized the allied strikes, saying they went beyond what the Arab body had supported.
"What happened differs from the no-fly zone objectives," Moussa told reporters in Cairo. "What we want is civilians' protection not shelling more civilians."
Nevertheless, France on Sunday said warplanes in the Arab Gulf nation of Qatar would participate in the campaign, a sign of continued Arab support.
The prospect of Gadhafi remaining in control of at least a portion of the country raises questions about how far the Obama administration and its European and other partners are willing to go with military force.
Obama referred to Libya but did not discuss the unfolding operation during remarks in Brazil.
"We've seen the people of Libya take a courageous stand against a regime determined to brutalize its own citizens," Obama said.
"No one can say for certain how this change will end, but I do know that change is not something that we should fear. When young people insist that the currents of history are on the move, the burdens of the past can be washed away."
Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, was pressed repeatedly during a round of Sunday television interviews to explain the mission's objectives. He said the main goal is to protect civilians from further violence.
"I think circumstances will drive where this goes in the future," the admiral said on ABC's "This Week." "I wouldn't speculate in terms of length at this particular point in time."
Asked whether it was possible that the military goals might be met without Gadhafi being ousted, Mullen replied, "That's certainly potentially one outcome." He described the Libyan strongman as more isolated than ever, adding that Gadhafi is "going to have to make some choices about his own future" at some point.
U.S. Secretary of State Hillary Rodham Clinton said that although ousting Gadhafi is not an explicit goal of the campaign, his departure might be hastened as the conflict continues.
"The opposition is largely led by those who defected from the Gadhafi regime or who formerly served it, and it is certainly to be wished for that there will be even more such defections, that people will put the future of Libya and the interests of the Libyan people above their service to Col. Gadhafi," she said.
Lucas reported from Benghazi, Libya. Associated Press writers Maggie Michael in Cairo and Lolita C. Baldor and Robert Burns in Washington contributed to this report.