The vandalism of the Muslim saints' tombs in the UNESCO World Heritage site came 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 UN's green light for the African-led military operation.
Planners have said any intervention cannot be launched before September next year. French Defence Minister Jean-Yves Le Drian however said in an interview due out in Monday's La Croix newspaper that he thought an intervention could occur in the first half of 2013.
In July, Islamists destroyed the entrance to a 15th-century mosque in Timbuktu, the so-called "City of 333 Saints."
"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 city, an ancient centre of learning and desert crossroads.
Ansar Dine first began destroying the cultural treasures in July.
The International Criminal Court warned 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 carried out amputations on two accused robbers 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 was making 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, though the Security Council vowed to keep working towards 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 advisor told AFP that the statements 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.
Meanwhile in Nigeria on Sunday, radical Islamist group Ansaru claimed last week's kidnapping of a French citizen in the north of that country. One reason he was targetted, said the group, was because of France's push for military intervention in northern Mali.
- AFP
