By John Irish
PARIS (Reuters) - Islamist rebels based in southern Libya were most likely to have been behind an attack on France's embassy in Tripoli last month, but there were no plans to intervene in the lawless desert region, President Francois Hollande said on Friday.
France, which led international efforts to oust Muammar Gaddafi in 2011, is concerned that foreign Islamist fighters who escaped after Paris' intervention in Mali in January are now regrouping in southern Libya.
Tripoli is struggling to control armed groups which helped topple Gaddafi and now refuse to lay down their weapons. Parliament in December declared the south a military zone but policing its borders remains a huge task for weak state forces.
France's embassy in the capital was targeted on April 23 with a car bomb that wounded two French guards.
Suicide bombers also attacked a French-run uranium mine in Niger last week, underscoring fears France's interests in the region will increasingly be targeted. Niger officials said they believed the attackers came from Libya's south.
Speaking in an interview with French media outlets France 24 and RFI, Hollande said nobody had been specifically identified for carrying the embassy attack, but for the first time pointed the finger at Islamist militants based in southern Libya.
"We think that this is the most likely (scenario)," he said. "We must see how we can cooperate with the Libyan authorities to nullify these terrorists."
Paris is keen to cut its troop numbers in neighboring Mali, but amid persistent bickering and mistrust among regional powers, Hollande said French forces may have to be used elsewhere in the Sahel.
However, he dismissed any suggestion Paris could intervene in Libya for now, saying that if any such operation were needed in the future it would need a U.N. mandate.
"I want to put an end to something that isn't information," he said when asked about the prospect of intervening.
The Malian crisis - where rebel groups seized the northern two thirds of the country last year, raising fears they could turn it into a base for militant attacks - was itself in part triggered by an influx of fighters originally armed in Libya.
Highlighting Paris' concerns, it is investing 20 million euros ($25 million) to increase security for diplomats and embassies in the Middle East and Africa after the car bombing.
France convened delegations from the United States, Britain, Arab nations, the United Nations and European Union to discuss ways to stabilize Libya in February. While Libya received pledges from several countries to provide technical support and equipment, little has materialized since.
"The only request we have had from the Libyans for help is to provide training and advice, as well as equipment to secure the borders," French Foreign Ministry spokesman Philippe Lalliot told reporters on Friday when asked whether Paris was considering military action in Libya.
Diplomats say that Libyan, French and regional governments are working on a number of initiatives to be announced over the coming weeks to help Tripoli to tackle its security void.
"We're extremely concerned that what's happening in southern Libya could replicate what happened in Mali. Dealing with that problem needs to be fast tracked," a French diplomatic source said.
(Editing by Alison Williams)