A suicide bomber was killed instantly when he accidentally detonated his explosives belt in the Malian rebel bastion of Kidal on Sunday, without killing or wounding anyone else, a local government official told AFP.

The incident came after militants carried out two attacks in northern Mali in less than 72 hours, marking an upsurge in violence since the breakdown of peace talks between the government and rebel groups on Thursday.

"The bomber was wearing his belt. He did something wrong, the belt exploded, and he was killed on the spot, before he could go on to commit a terrorist attack in the city," an official in the Kidal governor's office said.

"There was a big explosion that blew up part of the building the bomber was in."

An African military source said the explosion went off in a disused warehouse of the UN World Food Programme near the Kidal governor's official residence, currently occupied by Tuareg separatist rebels.

"I believe that the bomber came from outside the city. He came discreetly," he said, without elaborating.

The incident came after four suicide bombers blew up their car at an army barracks in Timbuktu on Saturday, killing two civilians and wounding six soldiers, and two days after two men threw hand-grenades at Malian troops, wounding two soldiers in Kidal.

Mali has suffered a series of attacks claimed by Islamist insurgents since France launched a military operation in January against Al-Qaeda-linked groups occupying the north of the country.

But no Islamist group has claimed any of the latest attacks, which followed the suspension of peace talks on Thursday between the government and Tuareg and Arab rebels who want autonomy for northern Mali.

The government urged Malians to remain calm after Saturday's attack, saying security was being enhanced across the country.

"The multiplication of these attacks shows that the war against terrorism is not over and that the security situation remains fragile throughout the Sahel-Saharan region," it said in a statement.

The National Movement for the Liberation of Azawad (MNLA) took control of Kidal in February after the French-led military operation ousted Al-Qaeda-linked fighters who had piggybacked on the latest Tuareg rebellion to seize most of northern Mali.

The Malian authorities reclaimed the city after signing a ceasefire deal with the MNLA but the situation has remained tense.