BAMAKO: Mali's army clashed with Islamist rebels along the front line in northern Mali on Thursday and said its forces had seized an important town, but the insurgents denied the claim.

The fighting is the first major attempt by government forces to push back the insurgents since they seized the north, including the fabled desert city of Timbuktu, last year and could squash hopes of peace talks.

Western and regional leaders fear the alliance of al Qaeda-linked rebels could use the vast desert zone, an area larger than France, as a launchpad to stage international attacks, and are planning a U.N.-backed military intervention.

Mali's army attacked rebel positions in Douentza, a gateway town between Mali's rebel-held north and government-held south that had been in the hands of the Islamists since September.

"The army has retaken Douentza, we just had confirmation that the jihadists have withdrawn following the clash," an officer at the military junta headquarters told Reuters on Thursday, asking not to be named.

But a spokesman for the rebels said they were still in the town and were also fighting Mali troops elsewhere in the region.

"We are currently battling Malian troops in Konna," Ansar Dine spokesman Sanda Ould Boumama told Reuters by telephone. Konna is about 120 km west of Douentza in the Mopti region, some 600 kilometres (375 miles) northeast of the capital Bamako.

"With God's help, we will dislodge them very soon. We are fighting them at the military camp and we will take Konna," Boumama said.

It was not immediately possible to verify independently which side was controlling Douentza. A resident said that, though the Islamists withdrew after heavy fighting, the army was not inside the town.

Another resident, who also requested anonymity, told Reuters that two vehicles carrying Islamists were still in the town.

Clashes involving heavy artillery were also reported in other localities in the Mopti region and in Konna, a senior army officer at the Mali defence ministry said.

The renewed fighting could quash hopes of a breakthrough at peace talks between the Malian government, the rebels and separatist Tuaregs which were scheduled to start in Burkina Faso on Thursday but have been postponed until Jan. 21.

Djibril Bassole, Burkina Faso's foreign minister and regional mediator in the crisis, on Thursday called on the parties to respect a ceasefire deal agreed on Dec. 4.

Ansar Dine, one of the main rebel factions, said last week it had ended the ceasefire deal because of international plans for a military intervention.

The United Nations has given the green light for an African-led military campaign to retake Mali's north, though logistical and other problems mean that is unlikely to start before September.

Once an example of democracy and development in turbulent West Africa, Mali was plunged into crisis by a March 2012 coup which allowed Tuareg rebels to seize the country's north, demanding an independent homeland, but their rebellion was hijacked by the Islamists.

Bickering in the southern capital among Mali's political elite over the duration and a roadmap to end the post-coup transition, is causing paralysis and hurting efforts to unite the country.

Thousands of people took to the streets in Bamako on Wednesday calling for an end to a political crisis caused by the March coup, blocking the city's two main bridges.

The government responded to the protest on Thursday by shutting down all schools in Bamako and Kati until further notice.