By John Irish and Elizabeth Pineau
PARIS (Reuters) - Western air forces, with Arab League approval, went into action in Libya on Saturday to curb attacks by Muammar Gaddafi's forces on the rebel stronghold of Benghazi, French President Nicolas Sarkozy said.
Sarkozy said an operation supported by France, Britain, the United States and Canada, and backed by Arab nations, was halting air attacks by Gaddafi's forces and would continue unless the Libyan leader ceased fire.
Five French aircraft -- two Rafale multirole war planes, two Mirage fighter jets and an AWACS surveillance aircraft -- were involved, a French military source told Reuters.
The French planes were also ready to strike Libyan tanks, Sarkozy said after hosting a meeting of world powers to coordinate an intervention authorised by th U.N. Security Council on Thursday.
"It's a grave decision we've had to take," Sarkozy said in a statement to the media after talks with British Prime Minister David Cameron, U.S. Secretary of State Hillary Clinton, Arab leaders, European Union representatives and European heads of state.
"Along with our Arab, European and North American partners, France has decided to play its part before history," he said.
It was unclear whether NATO and the EU were taking a role in coordinating the mainly French operation, although Italy offered the use of a NATO base near Naples, Prime Minister Silvio Berlusconi said.
Sarkozy has been at the forefront of a push to intervene in Libya in recent days as Gaddafi escalated his attacks on opposition rebels which France and others support.
"Those taking part agreed to put in place all necessary means, especially military, to enforce the decisions of the United Nations Security Council," Sarkozy said.
Cameron told reporters in Paris that Gaddafi's breaking of a ceasefire pledged on Friday made swift action essential.
"Colonel Gaddafi has made this happen. He has lied to the international community. He has promised a ceasefire. He has broken that ceasefire," he said.
"He continues to brutalise his own people and so the time for action has come," he added. It is better to take this action than to risk the consequences of inaction, which is the further slaughter of civilians by this dictator."
Germany is not participating in the joint operation, but Berlusconi did not rule out Italian planes being used.
"For the time being we are making the bases available, but if they request it, even military intervention (is possible)," Berlusconi told reporters.
READY TO INTERVENE
Sarkozy said military aircraft would counter any attacks by Gaddafi's planes on Benghazi and were also ready to intervene against armoured vehicles threatening unarmed civilians.
Shortly before he spoke, a French military source said French reconnaissance planes were flying over Libya, where Gaddafi's troops advanced into the outskirts of Benghazi.
"We are doing it to protect the civilian population from the murderous madness of a regime that in killing its own people has lost all legitimacy," Sarkozy said.
"There is still time for Colonel Gaddafi to avoid the worst, by acting without delay and without reservations in accordance with all the demands of the international community. The door of international diplomacy will open again the moment attacks end."
Sources close to the talks said earlier that only France, Britain and Canada were likely to take part in initial strikes, with any participation by the United States or Arab nations coming later.
A Canadian government spokesman said the country's fighter jets had only just reached the region and would need two days to prepare for any operation.
Iraq's foreign minister was at the talks, as was the Qatari prime minister and United Nations Secretary General Ban Ki-moon and German Chancellor Angela Merkel, even though Germany is not expected to participate in any action for now.
Determined to prove its diplomatic clout after its clumsy handling of the revolt in Tunisia, Paris has sought to lead a world response to the crisis in Libya, where Gaddafi's troops outgun rag-tag and poorly armed rebel forces.
Sarkozy was the first foreign leader to recognise the opposition and drop support for Gaddafi.
NATO ambassadors met in Brussels earlier on Saturday to discuss involvement by the 28-member military alliance in enforcing a no-fly zone, but no decision was taken.
A NATO diplomat said Britain, the United States and Canada were in favour of NATO taking a lead in any operation but said Paris was lukewarm on the idea.
"There could be a decision tomorrow saying that NATO will engage in a no-fly zone, but it's still not clear whether it will be a coalition of the willing, or a NATO operation," the diplomat said.
"France seems to have some problem with it being a NATO operation, given NATO's reputation in the Arab world as a result of Afghanistan and given that NATO is seen as an alliance dominated by the United States."
(Additional reporting by Andrew Quinn, Keith Weir, Daniel Flynn and Marie-Victoria Bufferry in Paris and David Brunnstrom in Brussels; Writing by Catherine Bremer; Editing by David Cowell)