BENGHAZI, (Reuters) – Allied warplanes have gone into in action to stop Libyan leader Muammar Gaddafi’s forces attacking the rebel-held city of Benghazi, French President Nicolas Sarkozy said on Saturday.

Gaddafi’s troops on Saturday morning pushed into the outskirts of Benghazi, a city of 670,000 people, in an apparent attempt to pre-empt military intervention expected after a meeting of Western and Arab leaders in Paris.

But as the meeting ended, Sarkozy announced that allied air forces had already gone into action.

“Those taking part agreed to put in place all necessary means, especially military, to enforce the decisions of the United Nations Security Council,” he 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.

A French military source said France had five warplanes operating over Libya, including an AWACS reconnaissance plane and four attack aircraft, two Rafales and two Mirages.

Military action could be halted at any time if Gaddafi stopped his forces attacking, Sarkozy said.

“Colonel Gaddafi has made this happen,” British Prime Minister David Cameron told reporters after the meeting. “He has lied to the international community, he has promised a ceasefire, he has broken that ceasefire … We cannot allow the slaughter of civilians to continue.”

France and Britain have taken a lead role in pushing for international intervention in Libya and the United States — after embarking on wars in Afghanistan and Libya — has been at pains to stress it is supporting, not leading the operation.

Clinton said the United States would bring its “unique capabilities” to bear to help its European and Canadian allies in enforcing a U.N. resolution passed on Thursday to end violence in Libya.

Gaddafi has said Western powers had no right to intervene.

“This is injustice, this is clear aggression,” government spokesman Mussa Ibrahim quoted Gaddafi as saying in a letter to France, Britain and the United Nations. “You will regret it if you take a step toward interfering in our internal affairs.”

The Libyan government blamed the rebels, who it says are members of al Qaeda, for breaking a ceasefire around Benghazi.

A large crowd of Gaddafi supporters waving green Libyan flags and portraits of the leader gathered outside his house in Tripoli, in an apparent move to discourage foreign airstrikes.

Defiant gunfire rang out in Tripoli after the French announcement, and Gaddafi supporters sped through its streets shouting slogans from car windows.

THOUSANDS FLEE BENGHAZI

A large plume of black smoke rose from the edge of Benghazi mid-afternoon, live television pictures showed, but it was not clear what was causing the fire.

Residents set up make-shift barricades with furniture, benches, road signs and even a barbecue in one case at intervals along main streets. Each barricade was manned by half a dozen rebels, but only about half of those were armed.

Hundreds of cars full of refugees fled Benghazi toward the Egyptian border after the city came under a bombardment overnight. One family of 13 women from a grandmother to small children, rested at a roadside hotel.

“I’m here because when the bombing started last night my children were vomiting from fear,” said one of them, a doctor. “All I want to do is get my family to a safe place and then get back to Benghazi to help. My husband is still there.”

In the besieged western city of Misrata, residents said government forces shelled the rebel town again on Saturday and they were facing a humanitarian crisis as water supplies had been cut off for a third day.

“I am telling you, we are scared and we are alone,” a Misrata resident, called Saadoun, told Reuters by telephone.

PLANE SHOT DOWN

As explosions shook Benghazi on Saturday morning, rebels said they were forced to retreat from the outskirts of the city, but later claimed victory after holding back the advance.

“We revolutionaries have taken control of four tanks inside Benghazi. Rebel forces have pushed Gaddafi’s forces out of Benghazi,” said Nasr al-Kikili, a lawyer who works for the rebel media center in Benghazi, as crowds celebrated by firing guns in the air and parading on top of a tank.

An unidentified warplane was shot down over Benghazi.

“I saw the plane circle around, come out of the clouds, head toward an apparent target, and then it was hit and went straight down in flames and a huge billow of black smoke went up,” Reuters correspondent Angus MacSwan said.

“It seems it was attacking the Benghazi military barracks.”

Al Jazeera said there were 26 dead and more than 40 wounded in Jala hospital in Benghazi, without giving further details.

U.S. President Barack Obama has made clear any military action would aim to change conditions across Libya, rather than just in the rebel-held east, by calling on Gaddafi’s forces to pull back from the western cities of Zawiyah and Misrata as well as from the east.

“Gaddafi must stop his troops from advancing on Benghazi, pull them back from Ajdabiya, Misrata and Zawiyah, and establish water, electricity and gas supplies to all areas. Humanitarian assistance must be allowed to reach the people of Libya,” Obama said on Friday.