Mali's army chief Tuesday said his French-backed forces could reclaim the northern towns of Gao and fabled Timbuktu from Islamists in a month, as the United States began airlifting French troops to Mali.

Malian forces patrolled Diabaly, about 400 kilometres (250 miles) north of Bamako, to buttress their presence after rolling into the central town on Monday along with French forces and getting a red carpet welcome by locals.

They also recaptured the strategic crossroads town of Douentza, which was seized by the Islamists in September.

The US military said meanwhile it has started airlifting French troops and equipment from France into Mali to assist their operation.

"We expect the mission to last for the next several days," an AFRICOM spokesman, Chuck Prichard, said in Germany. "As of yet we've had two flights that have landed and we anticipate more in the coming days."

Belgium, Britain, Canada, Denmark, Netherlands, Spain and the United Arab Emirates are also providing transport planes or helicopters required to help move the African and French troops around Mali's vast expanses.

France began its military operation on January 11 and has said it could deploy upwards of 2,500 troops which would eventually hand over control to a UN-sanctioned African force set to number some 6,000 soldiers.

General Ibrahima Dahirou Dembele said the French-backed army was forging ahead for "the total liberation of northern Mali," in an interview with French radio station RFI.

"If the support remains consistent, it won't take more than a month to free Gao and Timbuktu," he said, referring to two of three main cities along with Kidal, in the vast, semi-arid north which has been occupied for 10 months.

The Al Qaeda-linked Islamists have subjected these towns to strict sharia law, whipping smokers and drinkers, banning music, forcing women to wear veils and long robes, amputating the limbs of thieves and stoning adulterers to death.

A fabled caravan town on the edge of the Sahara desert, Timbuktu was for centuries a key centre of Islamic learning and has become a byword for exotic remoteness in the Western imagination.

Today it is a battlefield, overrun by Islamist militants who have been razing its world-heritage religious sites in a destructive rampage that the UN cultural agency has deplored as "tragic".

Dembele said troops from Niger and Chad were expected to come through Niger, which borders Mali on the east, and head to Gao, a key Islamist stronghold which has been pounded by French airstrikes.

"The intention of the enemy fighters is to withdraw into the hills around Aguelhok," a far northern town near the Algerian border, he said.

The army chief said soldiers found guilty of rights abuses would be summarily punished, after Human Rights Watch and Arab and Tuareg groups alleged that they were committing "atrocities" including murder.

"Any soldier committing atrocities against the civil population will be immediately withdrawn from the ground and taken to Bamako to be judged in a military tribunal," he said.

A major boost to the African force is a pledge by Mali's neighbour Chad to deploy 2,000 soldiers there.

The Chadian troops are battle-hardened, having quelled rebellions at home and in nearby countries such as the Central African Republic.

"They are seasoned soldiers in the desert contrary to the armies of the Economic Community of West African States" regional bloc, said Philippe Hugon from the well-known French think-tank, the Institute of International and Strategic Relations.

France swept to Mali's aid 10 months after it lost over half its territory to Islamists, amid rising fears that the vast northern half of the country could become a new Afghanistan-like haven for Al-Qaeda.

The crisis erupted when the nomadic Tuaregs, who have long felt marginalised by the government, launched a rebellion a year ago and inflicted such humiliation on the Malian army that it triggered a military coup in Bamako in March.

The Tuaregs allied with Islamist groups including Al-Qaeda in the Islamic Maghreb (AQIM) and seized control of huge swathes of territory including the main northern towns of Gao, Kidal and Timbuktu but they soon fell apart.

Their success in seizing a vast stretch of desert territory raised fears they could use northern Mali as a base to launch attacks on the region, Europe and beyond.