* France says it will use force if necessary to get guns off streets
* French troops trade fire with gunmen near the airport
* Life resumes in the capital as scale of the killing emerges
By Emmanuel Braun
BANGUI, Dec 9 (Reuters) - French troops in Central African Republic manned checkpoints in the capital Bangui on Monday and searched for weapons in an operation to disarm rival Muslim and Christian fighters responsible for hundreds of killings since last week.
Shooting erupted near the airport after gunmen refused to hand over their weapons, as France said it was prepared to use force if fighters rejected calls to disarm or return to barracks.
France boosted its military presence in its former colony to 1,600 troops over the weekend as waves of inter-religious violence swept across the country. At least 459 people have been killed in Bangui alone since Thursday, according to local Red Cross officials.
"This is not an easy job, but our soldiers are ... well prepared," French Foreign Minister Laurent Fabius told France Inter radio.
He said the order to disarm had been broadcast on local radio in Bangui, adding: "If that is not enough, force is going to be employed."
Chronically unstable Central African Republic has spiralled into chaos since mainly Muslim Seleka rebels seized power in March and embarked on months of looting, raping and killing. Seleka's leader, Michel Djotodia, installed as CAR's interim president, has lost control of his loose band of fighters.
EXCHANGE OF FIRE
Christian militias and gunmen loyal to ousted president Francois Bozize attacked Bangui on Thursday, the same day the U.N. Security Council authorised France to use lethal force to help African peacekeepers already struggling to restore order.
In an early test of France's resolve, its forces traded fire with suspected Seleka fighters near the airport on Monday.
It was not immediately known whether there had been casualties, and a spokesman for the French army joint staff in Paris called the incident "insignificant".
"For the moment, it's very clearly positive," Colonel Gilles Jaron said, adding that French troops had already arrested 10 men and seized weapons.
"Many armed elements who held positions in Bangui have left their positions to go back to their barracks," he said.
The arrival of French troops has been broadly welcomed in a city slowly emerging from a reign of terror that saw fighters, both Christian and Muslim, go door-to-door murdering civilians as they cowered inside.
"Yesterday we couldn't even come here to cross this road because the Seleka came and set up a base here," said a woman who gave her name only as Armelle. "Thank God the French came ... If there's peace, things will get better."
As French warplanes and helicopters flew low overhead, Bangui residents reappeared on the streets and some shops and market stalls reopened for the first time since last week.
However, the United Nations said it had counted some 72,000 people displaced by the violence currently staying in various sites around the city, including at the airport, where French troops and African peacekeepers have their base.
"There are still conflicts in some neighbourhoods. There's still killing," said Amy Martin, head of the U.N. aid agency OCHA in Bangui. "For now, we don't have the sentiment that people are ready to go home.
As relative calm returned to Bangui, information from elsewhere in the country, cut off from the capital since last week, began to trickle in.
A humanitarian worker in the town of Bossangoa said the number of dead there from several days of violence between Seleka and Christian "anti-balaka" militias formed in response to the violence had risen to 38.
In Bozoum, in the northwest, U.N. officials received reports of dozens of dead, and there was also violence in the nearby town of Bocaranga.
Humanitarian agencies and rights groups said the latest figures only reflected bodies that had been officially counted, and that the final death toll was likely to be significantly higher.
"We've spoken to a lot of people who have just buried their relatives in the back yard because they couldn't get out or didn't see the point of calling the Red Cross," said Joanna Mariner, a crisis expert with Amnesty International in Bangui.
(Additional reporting by Marine Pennetier, Joe Bavier and Bate Felix; Writing by Joe Bavier; Editing by)