'Terrorist kingpins' killed in Mali mountains: Hollande 

French President Francois Hollande said Wednesday that top Islamic extremist leaders hiding out in a northern Mali mountain range where French troops are deployed, had been killed.

"The terrorist kingpins have been destroyed" in the Ifoghas mountains, Hollande told reporters in Warsaw, but he did not make it clear if key commander Mokhtar Belmokhtar was among them.

Chadian President Idriss Deby Itno on Monday reiterated his belief that Belmokhtar had been killed during fierce fighting in recent days in the Ifoghas mountains on Mali's northeastern border with Algeria.

But French Defence Minister Jean-Yves Le Drian said Tuesday it was not clear that Belmokhtar, the mastermind of the January assault on an Algerian gas plant that left 37 foreign hostages dead, had been killed.

An Al-Qaeda in the Islamic Maghreb (AQIM) source who on Monday confirmed the death of another prominent militant, Abdelhamid Abou Zeid, insisted that Belmokhtar was still alive and fighting.

The French government has said Abou Zeid was "probably" dead, but admitted it had no evidence of his demise.

Hollande on Wednesday also said that his country would begin pulling its troops out of Mali as of April.

The "final phase" of the French intervention in the troubled west African country "will last through March and from April there will be a decrease in the number of French soldiers in Mali as African forces will take over, supported by the Europeans," Hollande said during a visit to Warsaw for a six-nation European Union defence summit.

French Foreign Minister Laurent Fabius said in early February that French troop numbers in Mali -- who now number around 4,000 -- would decrease "as of March, if all goes according to plan."

France also said Wednesday that a fourth French soldier had been killed during fighting against Islamist militants in eastern Mali, about 100 kilometres (60 miles) from the northern city of Gao.

Hollande paid homage in a statement earlier Wednesday to "the sacrifice of this soldier who carried out his mission to free Mali of terrorist groups with courage and devotion."

The French army said Wednesday that a dozen militants were killed in the fighting near Gao. Four Malian soldiers were also wounded.

France has suffered relatively few casualties during its operations in Mali, launched in mid-January to back up Malian forces against Islamist rebels who seized control of the country's vast desert north last year.

The French-led intervention quickly ousted the rebels from the north's main cities. But fighting has intensified in recent days as efforts focus on hunting down the militants in mountainous areas.