A suicide bomber has blown himself up in the northern Mali town of Gao - the country's first such case, sources say.The attacker approached a group of soldiers on a motorbike before detonating an explosive belt, injuring one of them, a Malian officer told AFP.Gao is the most populous city in northern Mali, which was captured by Islamist militants last year.Meanwhile, there are report of exchanges of fire between rival soldiers in the capital, Bamako.Heavily armed soldiers attacked a camp of elite paratroopers, leaving "many injured", a soldier insider the camp told AFP.A BBC reporter in the city said he had heard shooting. A Malian defence official told Reuters news agency the paratroopers had mutinied after being disciplined.France has sent some 4,000 troops to northern Mali to oust the militants.They have retaken control of the main towns, while most of the militants are reported to have fled to mountains near the Algerian border.On Thursday, there were unconfirmed reports that four Malian soldiers had been killed by a landmine on a road near Gao, with one of the militant groups saying it had carried out the attack.The militants took advantage of a coup in March 2012 to extend their control across the whole of northern Mali - an area of the Sahara Desert larger than France.Several different militant groups joined together to fight Mali's army - some ethnic Tuareg groups were fighting for independence for northern Mali, while others had an Islamist agenda and were allied to al-Qaeda, with reports of foreign jihadis joining them.