Islamist militants destroyed two tombs on Tuesday at the famous 14th century Djingareyber mosque in Timbuktu, classified by UNESCO as a world heritage site, residents said.

About a dozen militants arrived in an armored four-wheel drive truck, armed with pickaxes and hoes. They fired in the air to intimidate people and started smashing the tombs, said Ibrahim Cisse, who witnessed the scene.

“They blocked the two main roads leading to the mausoleums. When they saw people gathering for a ceremony nearby, they began firing shots in the air,” said another resident, Mahamad ould Ibrahim.

The new destruction comes after attacks last week on other historic and religious landmarks in Timbuktu that UNESCO called “wanton destruction”.

Islamists of the Ansar Dine group say the centuries-old shrines of the local Sufi version of Islam are idolatrous.

Ansar Dine and well-armed allies, including al Qaeda splinter group MUJWA, have hijacked a separatist uprising by local Tuareg MNLA rebels and now control two-thirds of Mali’s desert north, territory that includes the regions of Gao, Kidal and Timbuktu.

They have destroyed at least eight of 16 listed mausoleums in the city, together with a number of tombs and a sacred door at Sidi Yahya mosque, in their campaign to erase traces of what they regard as un-Islamic idolatry.

According to UNESCO, Djingareyber, together with the Sankore and Sidi Yahia mosques, are known as the three great mosques of the city. Djingareyber was built by the sultan Kankan Moussa after his return in 1325 from a pilgrimage to Mecca.