UN cultural agency UNESCO on Tuesday urged Malian and French forces fighting in Mali to protect ancient cultural sites during air raids and ground attacks.

"I ask all armed forces to make every effort to protect the cultural heritage of the country, which has already been severely damaged," UNESCO Director General Irina Bokova said in a statement.

French warplanes have been hitting targets in various parts of the country since Friday in support of Malian forces seeking to dislodge Islamist rebels who last year seized control of its vast desert north.

The rebels have since fled three key cities in the north, including Timbuktu, a UNESCO World Heritage site at a desert crossroads that was an ancient centre of learning.

The extremists last year smashed up mausoleums of ancient saints and the entrance to the 15th-century Sidi Yahya mosque in Timbuktu, claiming the sites were blasphemous.

"Mali's cultural heritage is a jewel whose protection is important for the whole of humanity," Bokova said.

"The destruction of World Heritage sites in Mali in 2012, especially the mausoleums in Timbuktu, sparked a wave of indignation across the world, helping to raise awareness of the critical situation facing the Malian people," she said.

"The current military intervention must protect people and secure the cultural heritage of Mali."

The statement said UNESCO had provided maps showing heritage sites to military planners as well as brochures to be handed out to soldiers on preventing damage to cultural heritage.