Backed by French air power, French and Malian forces quickly chased the jihadists out of the region's main towns, including the fabled Saharan city of Timbuktu.

But the intervention failed to restore peace to Mali.

Armed groups affiliated with the Islamic State group, Al-Qaeda and others advanced into the country's centre and south and into neighbouring Burkina Faso and Niger.

Seeking to stamp out jihadism in the Sahel, France launched a regional counter-terrorism operation, Barkhane, and prodded five countries -- Burkina Faso, Chad, Mauritania, Mali and Niger -- to set up their own joint G5 force.

But hopes that the G5 force would quickly take over, allowing France to bring its 4,500 Barkhane troops home, have been dashed by the African group's lack of funds, training and weaponry.

- Heavy losses -

The deaths of 13 French soldiers in the collision of two helicopters during an anti-terror operation in northern Mali on Monday brings to 41 the number of French troops killed in the region since 2013.

Of these, 10 were killed in the initial intervention in northern Mali with the rest killed in the ensuing six years of counter-terrorism operations.

Regional armies have also suffered heavy losses in the fighting.

In some of the deadliest incidents, Mali lost 24 soldiers during clashes with jihadists in the north-east last week. And in August, Burkina Faso lost 24 troops in an assault on a base near the Malian border.

The UN's 13,000-strong peacekeeping mission in Mali, MINUSMA, has also regularly come under attack. Since 2013, it has lost over 200 peacekeepers.

- 'Long-term' French fight -

During a visit to the region early this month, Defence Minister Florence Parly admitted that the security situation was "clearly difficult" but insisted there were no plans for a French pullout.

"The fight against terrorism is a long-term battle. We are armed with patience, determination and new ideas," she said.

After talks with his counterparts from Chad, Niger and Mali in Paris in mid-November, President Emmanuel Macron said France was "confirming and consolidating its commitment" to Operation Barkhane.

France is not the only Western power engaged in West Africa.

Britain is providing heavy-lift helicopters for Barkhane, the US is contributing intelligence support and funding for the G5 Sahel force and the European Union has been running a military training mission in Mali since 2013.

But the French are growing increasingly impatient with what they see as the low level of engagement by its European allies.

- Calls for European backup -

Speaking on RTL radio, French former airforce general Jean-Paul Palomeros said Tuesday that the latest French casualties showed the limitations of a "purely national" intervention.

"Our European friends, if they want to ensure their long-term security against terrorism and jihadism, must help us and step up now," he added.

Last year, the EU extended the mandate of the EU training force in Mali for two years, nearly doubled its budget and expanded its remit to training troops from all five countries engaged in the G5 force.

In the past few months, Paris has pressed its European partners to go further by sending special forces to shore up up the Sahel armies.

But by mid-October, only Estonia has stepped up, pledging in late September to send 50 soldiers.