By HADEEL AL-SHALCHI and RYAN LUCAS, Associated Press

TRIPOLI, Libya – A defiant Moammar Gadhafi vowed a "long war" after the U.S. and European militaries blasted his forces with airstrikes and over 100 cruise missiles, hitting air defenses and at least two major air bases early Sunday, shaking the Libyan capital with explosions and anti-aircraft fire.

Despite the strikes, Gadhafi's troops lashed back, bombarding the rebel-held city of Misrata with artillery and tanks on Sunday, the opposition reported.

The nighttime barrage, mainly by U.S and British ships and submarines, marked the widest international military effort since the Iraq war. The international air assault came as Gadhafi's overwhelming firepower was threatening to crush the month-old rebellion against his 41-year rule. State television said 48 people were killed in the strikes.

The strikes by missiles and warplanes hit 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, Gadhafi forces resumed bombarding Misrata after daylight on 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.

In Benghazi, the rebel capital and first city to fall to the uprising that began Feb. 15, people said the strikes happened just in time. Libyan government tanks and troops on Saturday had reached the edges of the city in eastern Libya in fierce fighting that killed more than 120 people according to Gibreil Hewadi, a member of the rebel health committee in Benghazi. He said the dead included rebel fighters and civilians, among them women and children.

Sunday, the city was quiet. As part of the international assault, French warplanes hit targets in the Benghazi area.

"It was a matter of minutes and Gadhafi's forces would have been in Benghazi," said Akram Abdul Wahab, a 20-year-old butcher in the city.

Mohammed Faraj, 44, a former military man who joined the rebels, held a grenade in each hand as he manned a checkpoint on the outskirts of the city.

"Me and all of Benghazi, we will die before Gadhafi sets foot here again," Faraj told The Associated Press. "Our spirits are very high."

The initial missile assault of 112 Tomahawk cruise missiles aimed to take out Gadhafi's air defenses to clear the way for enforcing a no-fly zone, targeting more than 20 radar systems, communications centers and surface-to-air missile sites. But the U.N. resolution authorizing the action goes much further, allowing "all necessary means" to protect civilians.

That means the U.S. and Europeans have a free hand in the next stages to attack Gadhafi's ground forces besieging rebel cities or other military targets.

The rebels, who control most of the eastern half of Libya, hope the allied intervention will — in the short term — tip the scales back in their favor after an onslaught by Gadhafi's forces threatened to reverse their gains early in the uprising. In the longer term, they hope to regain a momentum that will allow them to topple the Libyan leader.

Still, the top U.S. military officer said the goals of the international campaign are "limited" and won't necessarily lead to the ousting of Gadhafi.

Asked on NBC's "Meet the Press" whether it was possible that the mission's goals could be achieved while leaving Gadafi in power, Adm. Mike Mullen said, "That's certainly potentially one outcome." Pressed on this point later in an interview on CNN's "State of the Union," Mullen was more vague, saying it was too early to speculate. He said the Libyan leader is "going to have to make some choices about his own future" at some point.

Gadhafi vowed to fight on. In a phone call to Libyan state television, 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 ullulating, 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."

The cruise missile assault was the "leading edge" of a coalition campaign, named Operation Odyssey Dawn, said Navy Vice Adm. William E. Gortney, director of the Pentagon's Joint Staff.

He said it would take six to 12 hours to assess the damage, and if the main targets — Libya's SA-5 surface-to-air missiles — were taken out, then it would be safe to send an unmanned Global Hawk surveillance drone to get a better picture of the area.

French fighter jets fired the first salvos overnight, carrying out several strikes in the rebel-held east, around the Benghazi area, while British fighter jets also bombarded the North African nation. The cruise missile barrage was fired from five U.S. ships in the Mediterranean — the guided-missile destroyers USS Stout and USS Barry, and three submarines, USS Providence, USS Scranton and USS Florida.

The U.S. military announced that Navy electronic warfare aircraft and Marine Corps attack jets joined the international assault early Sunday. Navy EA-18G Growlers launched from unspecified land bases to provide electronic warfare support over Libya. Marine AV-8B Harriers from the USS Kearsarge sailing in the Mediterranean conducted strikes against Gadhafi's ground forces and air defenses.

President Barack Obama said military action was not his first choice and reiterated that he would not send American ground troops.

"This is not an outcome the U.S. or any of our partners sought," Obama said from Brazil, where he is starting a five-day visit to Latin America. "We cannot stand idly by when a tyrant tells his people there will be no mercy."  

 The U.S. has struck Libya before. Former President Ronald Reagan launched U.S. airstrikes on Libya in 1986 after a bombing at a Berlin disco — which the U.S. blamed on Libya — that killed three people, including two American soldiers. The airstrikes killed about 100 people in Libya, including Gadhafi's young adopted daughter at his Tripoli compound.

The overnight attack early Sunday shook coastal cities, including Tripoli, where anti-aircraft guns could be heard firing.

Libyan TV quoted the armed forces command as saying 48 people were killed and 150 wounded in the allied assault. It said most of the casualties were children but gave no more details.

Mullen told NBC's "Meet the Press" that he had seen no reports of civilian casualties as a result of the coalition's military operation.

The International Committee of the Red Cross said it was "deeply concerned" about civilians and called on all sides work to distinguish between civilians and fighters and allow safe access for humanitarian organizations.

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Lucas reported from Benghazi, Libya. Associated Press writers Maggie Michael in Cairo and Lolita C. Baldor in Washington contributed to this report.