Radical Islamists controlling northern Mali on Saturday took a bulldozer to an independence monument in Timbuktu, where they have destroyed several world heritage treasures in recent months, witnesses said. "At the moment I can see eight Islamists with a bulldozer. They are busy destroying Timbuktu's independence monument," one witness told AFP. "With the help of a tractor the Islamists are busy destroying the Timbuktu independence monument," said another witness, speaking to AFP by telephone. The extremists, who seized control of Mali's vast north following a disastrous coup in March, began a campaign of destruction of Timbuktu's cultural treasures in July that prompted an international outcry. They had already removed the head of a horse alongside the monument, as well as destroying the tombs of ancient Muslim saints and the "sacred door" to a 15th-century mosque. The radicals consider the tombs to be "idolatrous" and have also threatened to destroy the city's three ancient mosques, one of which dates back to 1327. Once considered one of Africa's most stable democracies, Mali has slid into chaos since the March 22 coup overthrew the government of president Amadou Toumani Toure. Tuareg rebels and a number of Islamist groups backed by Al-Qaeda in the Islamic Maghreb (AQIM) capitalised on the power vacuum in the south to seize an an area larger than France. But the Islamists then overran the Tuareg and have been imposing their strict version of sharia on areas under their control, arresting unveiled women, stoning an unmarried couple to death, publicly flogging smokers and amputating suspected thieves' limbs, according to residents and rights groups.