French troops have encircled a key Malian town to stop radical Islamists from striking closer to the capital, a French official said.

France is tripling the number of troops deployed to Mali to 2,500, part of the massive preparation for a land assault to dislodge Islamist extremists.

Islamic extremists have seized control of the strategic town of Douentza, moving much closer to government-held territory in central Mali.

The UN Security Council threatened sanctions against Islamist fighters in northern Mali and condemned the destruction of heritage sites in the ancient city of Timbuktu in a resolution passed today.