An Islamist suicide bomber blew himself up in Mali on Friday, the country's first such attack, as the rebels' turn toward guerrilla tactics and clashes between rival soldiers showed that the war is far from won.
An attacker rode a motorcycle 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 Islamist 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," MUJAO spokesman Abou Walid Sahraoui told AFP, vowing further attacks.
The turn to guerrilla warfare comes after French-led forces ousted extremist fighters from the towns under their control, sending many fleeing into the remote northeast, where troops Friday seized the strategic oasis town of Tessalit.
Some of the fleeing Islamists have also been spotted as far away as Sudan's troubled Darfur region, a Sudanese rebel commander said.
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 ousted in a March 2012 coup -- shot into the air in protest at an order absorbing them into other units to be sent to the frontline.
Two adolescents 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 tasked with whipping the Malian army into shape.
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".
The once stable nation imploded 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 counter-coup. 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, imposing a brutal form of Islamic law.
France launched a surprise intervention on January 11 in its former colony as the insurgents advanced towards the capital, raising fears the entire country could become a sanctuary for Al-Qaeda-linked groups.
France is now anxious to hand over the operation to UN peacekeepers amid fears of a prolonged insurgency.
MUJAO said 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, and French troops are still fighting off what Paris called "residual jihadists" in reclaimed territory.
-- UN chief wary --
UN leader Ban Ki-moon expressed concern Thursday.
"All these jihadis and armed groups and terrorist elements -- seemingly they have fled," he said. "Our concern is that they may come back."
After announcing plans to start withdrawing in March, France on Wednesday called for a UN peacekeeping force to take over, incorporating some 6,000 African troops slowly being deployed.
But Ban warned 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.
Continuing their advance Friday, French special forces parachuted into the airport at Tessalit, near the Algerian border in the far northeast, the army said.
Along with Chadian troops, they sought to flush the Islamists out of hiding in the Adrar des Ifoghas mountains, where they are believed to have fled with seven French hostages.
Former US ambassador to Mali Vicki Huddleston said France and other Western countries had paid as much as $89 million from 2004 to 2011 in ransom payments to the militants French troops are now fighting.
Analysts say they fund themselves through kidnapping, drug trafficking and smuggling.
French President Francois Hollande said there was "no question" of ransoms being paid to free the current hostages.