Tuareg-led Malian rebels opened a new front Thursday in an increasingly violent quest for independence that has killed dozens of people since the start of the year, military and civilian sources said Thursday.

The rebels hoisted their flag in the town of Lere near the border with Mauritania, about 600 km (370 miles) northeast of Mali's capital Bamako, according to a local civilian source.

They entered the town without a fight. There was no army presence. The army had moved a small unit from there yesterday, said the source, who had been in touch with Lere residents.

A Malian military official and a diplomat confirmed the information.

The separatist Tuareg National Movement for the Liberation of Azawad (MNLA), who stepped up their rebellion with attacks in the north and northeast last week, seeks independence for the north of the country. They say they include Malian Tuaregs who fought for Libya's late leader Muammar Gaddafi before his fall.

A spokesman for the rebels said Thursday at least 50 Malian soldiers have been killed during heavy fighting in Aguelhok, in the north of the country Tuesday.

We had some injured but no dead. We recovered about 50 bodies of Malian soldiers, Moussa Ag Acharatoumane, a Europe-based spokesman for the MNLA, said by telephone.

Mali's defence ministry confirmed the fighting in Aguelhoc Tuesday saying there were heavy casualties on both sides.

During the operations, significant losses, both human and material, were recorded from both sides, defence ministry's spokesman Colonel Idrissa Traore said in a statement without giving further details.

A Mali security source in Bamako told Reuters earlier on Thursday that dozens of Malian troops were killed during the clashes with the rebels in Aguelhok.

This is a turning point in the conflict, the Malian security source said, adding that after being pushed back during a previous clash, the rebels returned with reinforcements and the army, which ran out of ammunition, was forced to abandon their positions in Aguelhok Wednesday.

It was a real carnage. Dozens of dead and several vehicles were burnt, the source said, requesting not to be named.

Another Malian army officer, who also requested not to be named, said the troops were ordered to leave their positions in Aguelhok, a town of about 8,000 inhabitants, and move with civilians further south to the town of Kidal.

The MNLA is seeking independence for what it calls the Azawad territory in northern Mali. It launched a rebellion on January 16, shattering a peace that had held since 2009.

The MNLA's Acharatoumane said that the group would continue attacks until Mali withdraws its troops and accepts the Tuaregs' right to self-determination.

Tuareg nomads, who have fought several rebellions for a sovereign homeland in the Sahara desert, are believed by Malian authorities and other regional leaders to have received an influx of weapons and men in the aftermath of Libya's war.

The past week has seen several clashes in at least four towns and Mali's military said last week that its armed forces had killed 45 gunmen and lost two soldiers.

Both sides said there was fighting Thursday in the northeastern town of Anderamboukane close to the border with Niger after the rebels attacked Malian army positions.

France, Mali's former colonial power, urged both sides to cease fire immediately. The crisis will not be resolved by force or violence, the French foreign ministry told a news briefing Thursday.

(Additional reporting by David Lewis in Dakar; Writing by Bate Felix; Editing by Richard Valdmanis)