Thirteen soldiers have been confirmed killed following a collision between two French military helicopters during a night time operation on jihadists in Mali. It is the single greatest loss of military personnel since France intervened in 2013.

The deaths of the French troops in Mali resulted from a collision between a ‘Tigre’ and a ‘Cougar’ helicopter, according to a statement from the head of the French armed forces.

The statement added that the helicopters had been called in as reinforcement to back up French soldiers Mali.

“Thirteen French soldiers were killed in Mali when their helicopters collided at low altitude as they swooped in to support ground forces engaged in an counter-terror operation in Mali,” the French army said on Tuesday.

“They were supporting commandos from the Barkhane force who were engaged with armed terrorists,” the Defence Ministry said in a statement.

“The president announces with deep sadness the death of 13 French troops in Mali on the evening of November 25, in an accident between their two helicopters during a combat mission against jihadists,” a statement from Emmanuel Macron’s office said on Tuesday.

The fatalities included six army officers, six non-commissioned officers and a corporal, according to reports.

France currently has over 4,500 troops on the ground in Mali helping to fight against multiple jihadist insurgencies across the Sahel region. The UN has also stationed 15,000 troops there in addition to the French forces.

Militant groups aligned with both Islamic State and Al Qaeda have launched sporadic attacks across the sparsely populated region for years. Central and northern Mali in particular have been used as staging grounds for attacks in other countries in the past.

France was already reeling from the loss of Brigadier Ronan Pointeau who was killed in Mali earlier this month when an improvised explosive device detonated near his vehicle. Islamist militants killed dozens of Malian soldiers earlier this month in one of the deadliest attacks in the country’s recent history.

It was the biggest loss of French troops in a single day since an attack in Beirut 36 years ago when 58 soldiers died.