President Francois Hollande arrived in Mali on Saturday as French-led troops worked to secure the last Islamist stronghold in the north after a lightning offensive against the extremists.

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Hollande, whose surprise decision to intervene in Mali three weeks ago has won broad support at home, was to thank French troops who have pushed back the radicals from the north of Paris's former colony and to push for their speedy replacement by African forces.

"I am going to Mali to express to our soldiers all our support, encouragement and pride," he said a day before his visit. "I'm also going to ensure that African forces come and join us as quickly as possible and to tell them we need them for this international force."

Mali's interim president Dioncounda Traore met Hollande as he flew in to the central town of Savare accompanied by his foreign, defence and development ministers.

The two men were to hold a working lunch later in the day in the capital Bamako and Hollande was also due to visit troops in the fabled desert city of Timbuktu.

France is keen to hand over its military operation to nearly 8,000 African troops slowly being deployed in the country, which the United Nations is considering turning into a formal UN peacekeeping operation.

But there are mounting warnings that Mali will need long-term help to

address the crisis and fears that the Islamists, who have retreated in the face of French troops, will now wage a guerrilla campaign.

US Defense Secretary Leon Panetta said Friday that French forces had rolled back the Islamist militants "much faster" than the United States had expected but now face the daunting task of building long-term security in the region.

"They have made tremendous progress, I give them a lot of credit," Panetta told AFP in an interview at the Pentagon. "But the challenge now is to make sure that you can maintain that security and that you are not overstretched and that, ultimately, as you begin to pull back, that the other African nations are prepared to move in and fill the gap
of providing security."

In Timbuktu, Hollande is due to meet with troops and visit the 700-year-old mud mosque of Djingareyber and the Ahmed Baba library, where Islamists burned priceless ancient manuscripts before fleeing.

The trip comes as troops are poised to secure the sandy northeastern outpost of Kidal, the rebels' last bastion.

A first contingent of Chadian troops has now entered the town, a Malian security source said, and French soldiers are stationed at the airport, which they captured Wednesday.

The French-led campaign, provoked by a southward rebel advance that sparked fears the entire country could become a haven for Al-Qaeda-linked radicals, has claimed a rapid succession of victories in key Islamist strongholds.

But the joy of citizens throwing off the yoke of brutal Islamist rule, under which they were denied music and television and threatened with whippings, amputations and execution, has been accompanied by a grim backlash against light-skinned citizens seen as supporters of the Al Qaeda-linked radicals.

Rights groups have reported summary executions by both the Malian army and the Islamists, who capitalised on the chaos unleashed by a March coup to seize an area the size of Texas.

Human Rights Watch said Islamists were implicated in the execution of at least seven Malian soldiers, slitting their throats or shooting them in the
mouth.

It also said Malian troops had shot at least 13 suspected Islamist supporters in Savare and dumped them into wells, a report corroborated by other rights groups.

The Malian army has denied any crimes by its forces.