* Eighth soldier killed since January 2013 intervention
* France to deploy 3,000 troops in region against Islamists
* Sending experts to Nigeria to seek kidnapped schoolgirls
By John Irish
PARIS, May 8 (Reuters) - A French soldier has been killed in northern Mali as France prepares to deploy thousands of its troops across the region to better fight Islamist militancy, Defence Minister Jean-Yves Le Drian said on Thursday.
The soldier, the eighth to die in Mali since France intervened in its former colony in January 2013 to oust al-Qaeda linked militants controlling the north of the country, was killed after an explosive device went off under his vehicle, he told RMC radio.
Pockets of al Qaeda-linked fighters are still holding out across the north, more than a year after the French offensive aimed at driving them from the desert region they occupied for most of 2012 after hijacking a rebellion by Tuareg separatists.
But after being scattered across Mali and into neighbouring countries, they have now regrouped and stepped up operations in recent months, Le Drian said after announcing the death.
"A certain stability was achieved across the south (of Mali), but in the north a certain number of jihadists have wanted to regroup," he said. "They have nothing to lose. They will give up their life (for the cause)."
Le Drian said France was restructuring its forces across West Africa for more counter-terrorism activities to target Islamist groups taking advantage of porous borders between southern Libya, northern Chad and northern Niger.
"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," he said. "We will stay as long as necessary. There is no fixed date."
REDEPLOYED ACROSS REGION
France is particularly worried by the situation in Libya where more than two-and-a-half years after the fall of former leader Muammar Gaddafi, the oil-rich North African state is struggling to contain violence between rival forces and Islamist militants are gaining ground in the south.
French defence officials say the new phase in operations will allow their forces to operate freely across borders to strike militants. It was recently approved by the main countries concerned - Mauritania, Mali, Niger, Chad and Burkina Faso.
French forces will now be based in four regional centres. Some will be in Gao in northern Mali, others Niger's capital Niamey, where French surveillance drones are based, and in the Burkina Faso capital Ouagadougou, where until now special forces have launched raids into the desert.
The fourth centre will be in the Chadian capital N'Djamena, where the operations will be coordinated.
Smaller bases to launch strikes are also being set up with Abidjan in the Ivory Coast as the mission's logistical hub.
"This area is key to the security of African states," 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 this soldier)."
France, which also has more than 2,000 troops in Central African Republic, is sending about 10 intelligence experts to Nigeria to help find more than 200 schoolgirls kidnapped in April by Boko Haram.
With thousands of troops in the region, Paris has a major interest in preventing Nigeria's security from deteriorating and has voiced concern Boko Haram could spread north into the Sahel.
"We will provide our help to the Nigerian (intelligence) services to locate these girls are," Le Drian said. "We have the means to do that and eventually to help bring them back."
(Reporting By John Irish; Editing by Tom Heneghan)