* French troops secure Kidal airport, operation ongoing
* French, Malian forces already took Gao, Timbuktu unopposed
* Fabius says French troops will leave "very quickly"
By Richard Valdmanis
DOUENTZA, Mali, Jan 30 (Reuters) - French troops have taken control of the airport in the northern Malian town of Kidal, the last rebel stronghold in the north, the French army and a local official told Reuters on Wednesday.
Kidal would be the last of northern Mali's major towns to be retaken by French forces, which retook Gao and Timbuktu earlier this week in a campaign to drive al Qaeda-linked Islamists from Mali's north.
"They arrived late last night and they deployed in four planes and some helicopters," Haminy Belco Maiga, president of the regional assembly of Kidal said, adding he had seen no early indications of resistance from rebel forces.
French Armed Forces spokesman Thierry Burkhard confirmed in Paris that French troops were in Kidal and said they had taken control of the airport.
"The operation is continuing," he said, declining to give further details.
It was not immediately clear whether the French troops were accompanied by Malian forces.
Tuareg MNLA rebels who want greater autonomy for the desert north said earlier this week that they had taken control of Kidal after Islamists abandoned the town.
The MNLA, which fought alongside the Islamists before being sidelined by them in mid-2012, was not immediately available for comment on the French deployment.
Kidal is the capital of a desert region with the same name into which Islamist fighters are believed to have retreated during nearly three weeks of French air strikes and a joint advance by thousands of French and Malian ground troops.
The offensive in France's former West African colony is aimed at heading off the risk of Mali being used as a springboard for jihadist attacks in the wider region or Europe.
French troops, now numbering 3,500 on the ground, and Malian soldiers retook the Saharan trading towns of Timbuktu and Gao at the weekend virtually unopposed.
Doubts remain about just how quickly an African intervention force, known as AFISMA and now expected to exceed 8,000 troops, can be fully deployed in Mali to track down retreating al Qaeda-allied insurgents in the north.
French Foreign Minister Laurent Fabius said the French operation was planned to be a lightning mission that would last just a few weeks to avoid getting bogged down.
"Liberating Gao and Timbuktu very quickly was part of the plan. Now it's up to the African countries to take over," he told the Le Parisien daily. "We decided to put in the means and the necessary number of soldiers to strike hard. But the French contingent will not stay like this. We will leave very quickly."
Fabius warned that things could now get more difficult.
"We have to be careful. We are entering a complicated phase where the risks of attacks or kidnappings are extremely high. French interests are threatened throughout the entire Sahel," he said. (Reporting by Richard Valdmanis, John Irish and Emmanuel Jarry in Paris; Additional reporting and writing by David Lewis; Editing by Jon Boyle)