Armed groups occupying Timbuktu in northern Mali used pickaxes on Sunday to smash up any remaining mausoleums in the ancient city, an Islamist leader said.

The rebels' ruthless implementation of their version of Islamic law comes after the United Nations approved a military force to wrest back control of the conflict-ridden area.

"Not a single mausoleum will remain in Timbuktu, Allah doesn't like it," Ansar Dine leader Abou Dardar told AFP. "We are in the process of smashing all the hidden mausoleums in the area."

Witnesses confirmed the claims, which were also backed by a resident who said he belongs to Al-Qaeda in the Islamic Maghreb (AQIM), another militant group occupying the fabled city since a March coup plunged the west African state into chaos.

Anything that doesn't fall under Islam "is not good. Man should only worship Allah," Mohamed al-Foul said of the mausoleums that armed Islamists consider blasphemous.

The vandalism of the Muslim saints' tombs in the UNESCO World Heritage site followed a day after other Islamists in the northern city of Gao announced they had amputated two people's hands.

The continued strict application of Sharia law is seen as a sign that the armed Islamist groups are unfazed by the United Nations' green light for the African-led military operation, which planners say cannot be launched before September next year.

The Islamists destroyed the entrance to a 15th-century mosque in Timbuktu, the so-called "City of 333 Saints," in July.

"The Islamists are currently in the process of destroying all the mausoleums in the area with pickaxes," one witness said.

"I saw Islamists get out of a car near the historic mosque of Timbuktu. They smashed a mausoleum behind a house shouting 'Allah is great, Allah is great,'" another resident told AFP.

Not only present in cemeteries and mosques, the revered mausoleums are also found in alleyways and private residences in the fabled city, an ancient center of learning and desert crossroads.

Ansar Dine first began destroying the cultural treasures in July.

The International Criminal Court warned that their vandalism was a war crime, but the Islamists followed up with more damage in October, when they smashed several Muslim saints' tombs, prompting another international outcry.

The latest vandalism comes a day after another Islamist group in northern Mali — the Movement for Oneness and Jihad in West Africa (MUJAO) — said it had cut off the hands of two people in the northern city of Gao and warned of more to come.

Gao lawmaker Abdou Sidibe blamed the amputations on the "international community's laxness," saying its hesitation over whether to intervene to reconquer Mali's north were making the Islamists feel invincible.

"The international community needs to know that it is its hesitation over intervening, or no, in northern Mali that is encouraging the Islamists to show they are at home and are not afraid of anything," Sidibe said Saturday.

On Thursday, the United Nations decided to back the 3,300-troop operation to take back the Islamist-held region.

But the operation will not be launched before September next year, and the Security Council vowed in the meantime to work toward a peaceful solution.

On Friday, two of the armed rebel groups occupying the north — including Ansar Dine — denounced the UN approval of the intervention force and vowed to cease hostilities.

But a Malian presidential adviser told AFP that the statements, which were released on the day Ansar Dine carried out its latest amputations, contained nothing new.

Once considered one of Africa's most stable democracies, Mali has for months been mired in the northern conflict that has so far displaced more than 400,000 people, according to the United Nations.