PARIS: World leaders agreed Saturday at an emergency summit to a military intervention in Libya, with French fighter jets soaring over Benghazi to protect civilians from Moammar Gadhafi's forces and warplanes from other countries amassing around the Mediterranean.

France led the way with the first surveillance missions and the first strike, firing on a Libyan military vehicle, even before the joint military command was in place, according to French Defense Ministry spokesman Thierry Burkhard.

Warplanes from the United States, Canada, and Denmark arrived at Italian air bases Saturday. Germany backed the operation but isn't offering its own forces.

It was the first reported offensive military action against Gadhafi's troops since the UN Security Council approved a resolution on Thursday, authorising operations to protect civilians in Libya.

The strike came less than two hours after top officials from the United States, Europe and the Arab world agreed in Paris to launch a military operation to protect civilians from attacks by Gadhafi's forces.

It also came after Libyan government troops forces attacked Benghazi earlier Saturday, apparently ignoring a proclaimed cease-fire.

Canada's Prime Minister Stephen Harper, in Paris, said Gadhafi's claim of a cease-fire ''was an obvious lie from the beginning.''

The French airstrike hit at 1645 GMT Saturday and the target was confirmed as a military vehicle, but it was not clear what kind, Burkhard said. He said no hostile fire on the French jet has been reported.

France sent a dozen Mirage and Rafale jets Saturday to survey the one-time opposition stronghold of Benghazi and the 150 kilometer-by-100 kilometer no-fly zone, Burkhard said.

''All aircraft that enter into this zone could be shot down,'' he said. Top US, Arab and European leaders —22 participants in all representing dozens of countries —agreed at an emergency summit in Paris on Saturday ''agreed to put in place all the means necessary, in particular military'' to make Gadhafi respect a UN Security Council resolution Thursday demanding a cease-fire, French President Nicolas Sarkozy said.

US Secretary of State Hillary Rodham Clinton said the US will bring ''unique capabilities to bear'' in Libya.

British Prime Minister David Cameron said after the summit: ''The time for action has come, it needs to be urgent.''

UN Secretary General Ban Ki-moon hailed Saturday's meeting as a success. ''Arab countries, Europeans, Americans —they were all in one voice.''

Germany's Chancellor Angela Merkel said she backed the operation but added, ''We will not participate with our own soldiers.''

Harper was among those acknowledging the risks involved in such an operation. ''We should not kid ourselves,'' he told reporters in Paris. ''One cannot promise perfection, or that there will not be casualties on our side.''

But he added, ''We're dealing with a regime that will not be satisfed with the reimposition of its authority. ... They will massacre every single individual they remotely suspect of disloyalty.''

The incursion into Benghazi and other cities by Gadhafi's forces could vastly complicate any international intervention, by allowing the troops to mingle in with the population _ making airstrikes against them difficult.

''In accord with our partners, our air forces will oppose any aggression by Col. Gadhafi's airplanes against the population of Benghazi. Already, our planes are preventing air attacks against the city. Already, other French planes are ready to intervene against tanks that would threaten unarmed civilians,'' Sarkozy said in a brief declaration.

Sarkozy acknowledged the risks of the operation, and insisted it did not amount to an international occupation force.

''There is still time for Col. Gadhafi to avoid the worst by complying without delay and without reservations to all the demands of the international community. The door of diplomacy will reopen at the moment when the aggressions cease,'' Sarkozy said.

Several countries clarified their possible participation in any armed intervention, laying out how long it would take for national forces to join in air strikes or surveillance overflights.

Six Danish F-16 fighter jets landed Saturday at the US air base in Sicily, and American F-18s and Canadian CF-18 Hornets were in the region.

Italy has offered the use of seven air and navy bases already housing US, Nato and Italian forces. Sigonella's size and close proximity to Libya makes it a key staging point.

France, Britain and the United States were among the major backers of a muscular UN Security Council resolution passed Thursday that authorizes a no-fly zone over Libya and ''all necessary measures'' to protect civilians.

Among those at the Paris summit were Arab League Secretary-General Amr Moussa and Qatar's emir Sheikh Hamad Bin Khalifa Al Thani and foreign ministers of Jordan, Moroccan and the United Arab Emirates.