KIDAL–  A suicide bomber rammed his explosives-laden vehicle into a checkpoint in the northern Malian city of Kidal Tuesday, killing at least four other people, military sources said.The attack struck a checkpoint manned by Tuareg separatists supporting the French-led military offensive against Islamist insurgents."The suicide attack targeted the checkpoint on the eastern side of Kidal which is manned by the MNLA (National Movement for the Liberation of Azawad),” a French military official told AFP in Gao, the main city in northern Mali.Several other officials confirmed the blast was an attack following an initial report that it may have been a controlled explosion of ammunition seized from the Islamist insurgency.The Islamic Movement for Azawad (MIA), another armed group, said its own fighters were also on duty at the targeted checkpoint and up to six of them might have been killed in the blast."An explosion at a military roadblock held by the MIA has left four to six dead in our ranks,” Alghabass Ag Intalla, whose group is a moderate splinter of the Al-Qaeda-allied Ansar Dine group, told AFP."Suicide attackers did this. They are against us and against the French,” he said.A local government official speaking on condition of anonymity said the attack occurred on the road leading to Menaka and confirmed the death toll."There were at least four victims... Everybody is afraid here in Kidal. The car bomb came from the centre of Kidal. That’s scary, we don’t know how many other car bombs are waiting in there,” he said.Kidal lies close to 1,000 miles (600 miles) northeast of the Malian capital Bamako and the nearby Ifogha mountains has been a key hideout for Al Qaeda-linked fighters, who were forced out of cities in the weeks following France’s January 11 intervention.Overwhelmed by the superior fire-power of the French air force and special forces, Islamist hardliners have pulled out of the towns they ruthlessly ruled for nine months, imposing an extreme form of sharia.They regrouped and reverted to guerrilla tactics, launching hit-and-run attacks against French or pro-government forces and resorting to suicide attacks.