* Suspected Islamist bomber causes no other casualties
* Army says troops move towards Tuareg stronghold
* Tuareg spokesman says fighters will respond if attacked (Adds extension of state of emergency)
A suspected Islamist suicide bomber blew himself up but caused no other casualties in an attack in the northern Malian town of Kidal, the bastion of Tuareg separatist MNLA rebels, witnesses said on Tuesday.
A day after the government accused the MNLA of ethnic violence in Kidal, the Malian army said its troops were moving towards the town. The government has vowed to return its troops to Kidal before a presidential election next month.
A French-led military offensive launched in January succeeded in ending a year-long occupation of Mali's desert north by al Qaeda-linked insurgents, ousting them from urban areas.
But Islamist attacks persist, usually targeting Malian soldiers and African forces deployed to the north. Seven people were killed in a suicide bombing in Kidal in February, and three soldiers from Chad died in another attack there in April.
The government announced on Tuesday it was extending a nationwide state of emergency, announced in January, until July 5. It will end before the official start of the election campaign.
Moussa Ag Ibidas, an aid worker in Kidal who heard Tuesday's explosion, told Reuters: "When we arrived, there was just human debris left. We couldn't even identify the body. His bomb must have been poorly programmed, or he made a false move."
Witnesses said the blast occurred near the Kidal home of an MNLA officer and not far from the former residence of Iyad Ag Ghaly, the leader of Islamist group Ansar Dine. It was unclear what the bomber had intended to target.
"FIGHT TO THE END"
The MNLA rose up last year, calling for the creation of a Tuareg homeland. The group later joined forces with al Qaeda-associated fighters as they rapidly overran the north, but was eventually sidelined by the better-armed Islamists.
The MNLA was not targeted by the French offensive and has since been able to retake some areas, including Kidal, that had been lost to the Islamists. This has strained relations between France and the transitional government in the Malian capital, Bamako.
The government accused the MNLA on Monday of violence against non-Tuaregs in Kidal and said the army would retake the city before the July 30 election. The MNLA denied the accusations of ethnic attacks.
It had previously set a mid-May deadline to take back control of the town.
A spokesman for the Malian army, Colonel Souleymane Maiga, said on Tuesday that Malian forces were moving towards Kidal.
"The army is on offensive reconnaissance. This means that we are putting troops in a favourable position should there be any offensive," Maiga said.
The MNLA has rejected Bamako's calls for it to lay down its weapons, saying it would resist any attempt to retake Kidal. It has said it is open to negotiations with the government if northern Mali's right to self-determination is recognised.
A Burkina Faso-based spokesman for the MNLA said its fighters would respond if attacked by Malian forces.
"We do not understand why they want to attack us when we want to negotiate for peace," Mossa Ag Attaher said.
"If they attack us the negotiations will not serve any purpose ... We will respond and fight to the end."