The ambush, which involved a car bomb explosion followed by gunfire, took place two days after militants killed at least six people during a raid on a military headquarters in central Mali.
An attack on a military patrol in northern Mali on Sunday killed four civilians and wounded 31 other people including eight French soldiers, Mali's security and defence ministries said.
The ambush, which involved a car bomb explosion followed by gunfire, took place two days after militants killed at least six people during a raid on a military headquarters in central Mali, a country where French troops are helping combat militant activity across its vast desert reaches.
The deteriorating security situation one month ahead of presidential elections points to the difficulty international partners face restoring peace in Mali, which has become a launchpad for attacks by groups linked to al Qaeda and Daesh across West Africa.
"From hospital sources, the provisional record after the suicide attack against a Barkhane patrol in Gao today...was 4 civilians dead and 31 seriously injured, including 8 from Barkhane," Mali's security ministry said on Twitter. Barkhane is the name of the near 4,000-strong French force stationed in its former colonies across the Sahel region.
A spokesman for the defence ministry confirmed the figures.
"I confirm that it was a car bomb that drove into a joint Barkhane/Malian army patrol," Boubacar Diallo said.
No claim of responsibility
Photos posted on social media showed black smoke billowing from an armoured vehicle surrounded by debris on a sandy road.
No one has claimed responsibility for the attack. But violence by Islamist militants has spread across the sparsely-populated Sahel in recent years, slowly taking back control lost when French forces knocked back an uprising by Tuareg rebels and militants in 2013.
Western powers have provided funding to a regional force made up of soldiers from Mali, Niger, Burkina Faso, Chad and Mauritania combating jihadists. But the so-called G5 force has been hobbled by delays disbursing the money and poor coordination between the five countries.
French President Emmanuel Macron, who last year complained that G5 was taking too long to set up, is due in Mauritania on Monday to discuss security in the region.
France's army spokesman, Patrik Steiger, confirmed that civilians had been killed on Sunday and the army was assessing the state of the 30-strong French patrol that came under attack.
He said the explosion happened near three French vehicles.