Heavy gunfire broke out on the streets of Gao in northern Mali today as a battle erupted between Malian troops and Islamist militants near the central police station.
Gao had been retaken just over two weeks ago by French and Malian forces, who supposedly drove out the militants.
But fears of suicide bombings were raised by the discovery of industrial-strength explosives in Gao earlier in the week.
And on Friday those fears were realised when a suicide bomber blew himself up at a checkpoint on the city's outskirts.
Only the bomber was killed, but it led to concerns over the Islamists' future strategy.
And a second suicide bombing at the same location late on Saturday highlighted fragile security in zones recaptured by the French-led offensive.
French forces rushed reinforcements and armoured vehicles to the Malian army checkpoint on Gao's northern outskirts.
Malian army officers said the checkpoint had come under attack by a group of Islamist rebels who fired from a road and bridge.
"Our soldiers came under heavy gunfire from jihadists from the bridge," said Malian Captain Sidiki Diarra.
"At the same time, another one flanked round and jumped over the wall. He was able to set off his suicide belt."
Security has been tightened in the wake of the suicide bombings, with military patrols stepped up and new checkpoints put in place.
Defence Minister Yamoussa Camara said on Saturday that Malian soldiers were still fighting jihadists in their desert hideouts just outside Gao.
At least two Islamists had been killed during fighting that took place several miles outside the town on Friday, he claimed.
"We call on the population of Gao to not give in to panic and above all to co-operate with defence and security forces to drive out the terrorists who are trying to infiltrate among civilians," said Mr Camara in the capital Bamako.
The young man who blew himself up on Friday had been living at a house in Gao that was a suspected jihadist hideout.