French fighter jets carried out "several strikes" in Libya Saturday, while the United States and Britain launched more than 100 missiles at the Gadhafi regime's air defences, ushering in the broadest international military campaign since the Iraq war.

U.S. President Barack Obama said the move "is not an outcome the U.S. or any of our partners sought." But foreign countries "cannot stand idly by when a tyrant tells his people there will be no mercy," he said from Brazil.

The U.S. and British navies launched cruise missiles at 20 military sites along the Libyan coast, according to the Pentagon. Many of the targets were located in the west of the country, where Libyan leader Moammar Gadhafi's forces are based.

British Prime Minister David Cameron said that his country's military forces were also "in action" over Libya. The offensive is being led by a five-member coalition that also includes Canada and Italy.

About 20 French fighter jets carried out airstrikes earlier on Saturday, military spokesman Thierry Burkhard told The Associated Press. The planes fired the first shot at a military vehicle belonging to Gadhafi forces, he said.

Libya's long-time leader pledged to protect his country from what he described as "crusader aggression" and Libyan state TV claimed that 48 people had been killed in the strikes, although that could not be independently verified. The sound of anti-aircraft fire and explosions were also reported in the capital of Tripoli overnight.

The coalition assault began shortly after French President Nicolas Sarkozy spoke at an emergency military meeting in Paris earlier on Saturday.

"Col. Gadhafi can avoid the worst by complying immediately and unreservedly with all the demands of the international community," Sarkozy told reporters. "The doors of diplomacy will open once again when the aggression stops."

The summit's 22 participants included UN Secretary-General Ban Ki-Moon and the foreign ministers of Jordan, Morocco and the United Arab Emirates.

Sarkozy said they had agreed "to put in place all the means necessary, in particular military" to make Gadhafi respect a UN Security Council resolution demanding an end to attacks on civilians and rebel forces in the country.

"Alongside its Arab partners, European partners and North American partners, France is resolved to shoulder its role before history," Sarkozy said.

On Thursday evening, the UN Security Council adopted a resolution that called for an immediate ceasefire in Libya, authorized the creation of a no-fly zone and compelled UN members to use "all means necessary" to protect civilians and stop the fighting. However, the resolution stopped short of allowing a ground invasion.

New fighting

Gadhafi has warned Western countries not to get involved in Libya's affairs, even as he continued a barrage on the rebel-held city of Benghazi on Saturday.

Prior to the coalition's military strikes, forces loyal to Gadhafi swarmed the rebel stronghold in eastern Libya on Saturday, attacking with warplanes, artillery and gunfire. Buildings shook from the impact of incoming shells and fighting was gradually moving closer to the centre of the city.

One of Gadhafi's warplanes appeared to have been shot down, though the Libyan government denied the incident. Journalists in Benghazi reported hearing apparent air strikes in progress immediately before the plane went down.

Rebel fighters celebrated the plane crash, while Benghazi residents built makeshift roadblocks out of bed frames and other scrap metal in anticipation of further fighting in the opposition-controlled city. Young men scrounged for bottles with which to make gasoline bombs.

"This city is a symbol of the revolution," said Essam Gheriani, a spokesman for the opposition. "It's where it started and where it will end if this city falls."

A doctor in the eastern city said 27 bodies had reached nearby hospitals early Saturday afternoon. But the fighting quieted by evening.

The rebel movement, which began Feb. 15 and seeks to oust Gadhafi, has suffered a series of recent defeats in the face of superior firepower by regime forces.

Speaking from Brazil, U.S. President Barack Obama said his country was united in the need for military action.

"Our consensus was strong and our resolve is clear," he said. "The people of Libya must be protected and in the absence of an immediate end to the violence against civilians our coalition is prepared to act and to act with urgency."

Other countries were also preparing for an assault on Saturday, moving fighter jets into position around the region, where Gadhafi continued a barrage on rebel strongholds

Six Danish F-16 fighter jets landed at the U.S. air base in Sigonella, Sicily, on Saturday. Danish officials said the jets would be ready for operation by Sunday.

Italy has committed the use of seven military bases for the operation against the Libyan dictator; the country's proximity makes Italy an ideal staging point for an international offensive.

Prime Minister Stephen Harper said Canada fully supported the need for immediate action.

Canada has committed six CF-18 fighter jets to help enforce the no-fly zone; a spokesman said the jets were moving to the region, but would not be ready for use for two days.

The Libyan government denied that it had shelled any towns Saturday, and alleged that it was the rebels that had broken a ceasefire called in haste by the Gadhafi regime the day before.

"Our armed forces continue to retreat and hide, but the rebels keep shelling us and provoking us," government spokesperson Moussa Ibrahim told The Associated Press.

Warning issued

France, Britain and the United States -- with the backing of unspecified Arab countries -- warned Gadhafi on Friday evening to pull his forces out of Benghazi and for them to withdraw from the cities of Misrata, Ajdabiya and Zawiya.

If residents of these cities do not have services restored and if they do not receive humanitarian aid, the Western powers warned that Gadhafi will "suffer the consequences" of military action.

In Tripoli, thousands of regime supporters gathered inside the Bab al-Aziziya military camp where Gadhafi lives, apparently hoping to protect it against attacks. Libyan TV also showed a crowd of Gadhafi supporters at the airports in Tripoli and in his hometown of Sirte.

Meanwhile the Libyan leader had a spokesperson deliver a public warning to Western powers not to get involved in the conflict.

"Libya is not yours. Libya is for the Libyans. The Security Council resolution is invalid," the spokesperson said at a press conference, reading the text of a Gadhafi-penned letter that was directed at Sarkozy, Cameron and UN Secretary-General Ban Ki-moon.

"You will regret it if you dare to intervene in our country."

In a separate letter, Gadhafi asked what U.S. President Barack Obama would do if he faced a similar uprising in America.

"If you had found them taking over American cities with armed force, tell me what you would do?"

With files from The Associated Press