A suicide bomber has blown himself up in Mali, the West African country's first such attack and a sign that the al-Qaeda-linked fighters are shifting towards guerrilla tactics.

The attacker rode a motorcycle on Friday up to an army checkpoint in Gao, the largest town in the north, and detonated an explosive belt, wounding one soldier, an officer said.

The young Tuareg was dressed as a paramilitary officer and also carried a larger bomb that failed to detonate.

The attack was claimed by the Movement for Oneness and Jihad in West Africa (MUJAO), one of a trio of armed groups that occupied northern Mali for 10 months before France sent in fighter jets, attack helicopters and 4,000 troops to drive them out.

"We claim today's attack against the Malian soldiers who chose the side of the miscreants, the enemies of Islam," Abou Walid Sahraoui, MUJAO spokesman, told the AFP news agency, pleding further attacks.

MUJAO said on Thursday it had "created a new combat zone" in Mali by organising suicide bombings, attacking military convoys and placing landmines.

Two Malian soldiers and four civilians have already been killed by landmines.

'Sad spectacle'

The turn to guerrilla warfare comes after French-led forces ousted fighters from the towns under their control, sending many fleeing into the remote northeast, where troops on Friday seized the strategic oasis town of Tessalit.

Despite the successes of France's offensive, the Malian state and military remain weak and divided, a situation highlighted by a gunfight in Bamako between rival troops.

The firefight erupted after paratroopers loyal to ex-President Amadou Toumani Toure, who was toppled in a March 2012 coup, shot into the air in protest at an order absorbing them into other units.

Two people were killed, according to state television, and another 13 people were wounded, the army said.

A paratrooper said women and children had been present, but it was not clear whether they were among the casualties.

Interim President Dioncounda Traore reprimanded the military over the "sad spectacle", saying "the Malian army no doubt has better things to do than what they were involved in today".

The fighting overshadowed the arrival of 70 EU military instructors, the first of an eventual 500-strong mission. French general Francois Lecointre, who is leading the mission, said there was "a real need to recreate the Malian army, which is in a state of advanced disrepair."

Concern over insurgency

After announcing plans to start withdrawing in March, France on Wednesday called for a UN peacekeeping force to take over, incorporating about 6,000 African troops slowly being deployed, amid fears of a prolonged insurgency.

Expressed his concern on Thursday, Ban Ki-moon, the UN secretary-general, said: All these jihadis and armed groups and terrorist elements, seemingly they have fled.

"Our concern is that they may come back."

He cautioned that it would take weeks for the Security Council to decide the next move, and officials said Mali's government had yet to accept a UN force.

For his part, Jeffrey Feltman, the UN political chief, said on Friday the organisation will work hard to help Mali hold "credible and legitimate" elections by the end of July.

He said the French-led military intervention was crucial to reunifying the country but real political reconciliation was critical to stabilising Mali and elections will be key.

Political differences

Feltman said political differences led to the March 2012 coup and those must be resolved.

The French intervention "has sidelined some of the military actors who I think had the idea of continuing to interfere in politics", he said.

He said he did not believe the leader of the 2012 coup, Captain Amadou Sanogo, "has quite the monopoly on power that he might have had a few months ago thanks to all the new engagement inside the country".

Mali was destabilised last year after the coup, carried out by soldiers stung by their humiliation at the hands of fighters from the nomadic Tuareg waging a separatist rebellion in the north.

A month later, paratroopers launched a failed countercoup. Fighting between feuding factions left 20 people dead.

With Bamako in disarray, al Qaeda-linked fighters hijacked the Tuareg rebellion and took control of the north, leading to the French intervention.