BAMAKO, Mali — A suicide bomber blew himself up at a checkpoint in northern Mali early Friday, the first known attack of its kind since the launch of the French-led offensive against Islamist rebels.

The attack by a teenager occurred in the city of Gao, authorities said. One Malian soldier was killed.

“The man approached the soldiers at the checkpoint on a motorbike. As soon as he got close, he set off the bomb,” said Capt. Oumar Maiga, a spokesman for the Mali army. “He was Tuareg.”

French troops launched the effort to flush out militants in the north last month.

Along with Malian forces, they liberated Gao two weeks ago, pushing militants who had controlled it since last year into nearby villages.

Despite the freedom, some militants lingered, hiding among the residents in the villages.

“Unfortunately, we expected the Islamists to return to these type of attacks as they were driven out of the city,” said Lt. Col. Philippe at the French army base in Gao.

The attack is the latest setback for Malian forces. Three weeks ago, three soldiers were killed when they hit a mine near Douentza in the central region.

The monthlong French offensive has killed “hundreds” of Islamist fighters in Mali, the French defense minister said this week, as his troops prepared to start withdrawing.

France, Mali’s former colonizer, has said it expects to begin pulling out its troops in March and leave African forces in control.

Despite the withdrawal, troops will continue operations to flush out militants in “some terrorist havens” in northern Mali, French officials said.

France launched the offensive against militants in Mali last month. The ground and air campaign has sent Islamist fighters who had seized the northern region fleeing into the desert and rugged terrain nearby.

French-led troops now control Timbuktu and Gao, along with a swath in between the two that was an Islamist stronghold for almost a year.

Islamic extremists carved out a large portion of the north last year after a chaotic military coup.

They banned music, smoking, drinking and watching sports on television, and they destroyed historic tombs and shrines in the region. World leaders feared that the al Qaeda-linked militants would turn the area into a terrorist haven.