France will deploy 3,000 troops to fight militant Islamists across Africa's vast Sahel region, the defence minister has said.
The region was a "danger zone", with militants regrouping in northern Mali, Jean-Yves Le Drian said.
France was therefore reorganising its forces to "pursue counter-terrorism" across several states, he said.
French forces helped the Malian government recapture the north from al-Qaeda-linked militants last year.
It said at the time it would reduce its troop presence in Mali from around 4,500 to 1,000.
A French soldier has been killed in the north of Mali after an explosive device went off under his vehicle, Mr Le Drian also said on Thursday.
He is the eighth French to be killed since France deployed troops to Mali in January 2013.
"There will be 1,000 soldiers that remain in Mali, and 3,000 in the Sahel-Sahara zone, the danger zone, the zone of all types of smuggling," Mr Le Drian said, in a television interview.
"We will stay as long as necessary. There is no fixed date," he added.
French forces will be based in four regional centres - Mali, Chad, Niger and Burkina Faso - Reuters news agency reports.
Smaller bases from which to launch strikes are being set up, with Ivory Coast as the mission's logistical hub, it adds.
"This area is key to the security of African states," Mr Le Drian said. "But it is also for our own security. We have to prepare for the risks because they are very big and we see that again today with the death [of the soldier]," he said.
West Africa analyst Paul Melly told the BBC that it would be hugely difficult to completely eradicate the militant groups — for whom lawless southern Libya effectively provides a safe haven.
But he says the reinforced French deployment will be able to react quickly in crisis situations and should be able to hamper the ability of the remaining jihadist bands to launch fresh attacks.
The United Nations has more than 6,000 troops in Mali to help the weak government that took power in elections in August 2013.