Two more tombs at the Djingareyber mosque in Timbuktu have been destroyed by the Ansar Dine group.
The BBC reports shots were fired in the air to warn people away as fighters from the group began smashing the shrines.
Timbuktu is a World Heritage site. Ansar Dine says the shrines are idolatrous and wants them removed.
The group has destroyed a number of mausoleums in the city, and has vowed to smash them all. Its fighters have also broken down the door of the 15th-Century Sidi Yahia mosque.
The UN Security Council condemned the destruction last week of some shrines, warning it could constitute a war crime.
The BBC says this means that a case could be referred to the International Criminal Court in The Hague.
Ansar Dine is linked to al-Qaeda. Its forces seized the city in April.