A suicide bomber has attacked a checkpoint in northern Mali, killing only himself, in the first known suicide bombing since French military forces intervened in the country.

The US airlift of French forces to Mali to fight Islamic extremists is expected to go on for another two weeks, Pentagon officials said, as hundreds of African troops join the French-led intervention.

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