FILE - In this May 19, 2017 file photo, a French soldier stands inside a military helicopter during a visit by French President Emmanuel Macron to the troops of Operation Barkhane, France's largest overseas military operation, in Gao, northern Mali. French President Emmanuel Macron said Tuesday Nov.26, 2019 a midair collision between two helicopters has killed 13 French soldiers fighting against Islamic extremists in Mali. (Christophe Petit Tesson, Pool via AP, File)

FILE - In this May 19, 2017 file photo, a French soldier stands inside a military helicopter during a visit by French President Emmanuel Macron to the troops of Operation Barkhane, France's largest overseas military operation, in Gao, northern Mali. French President Emmanuel Macron said Tuesday Nov.26, 2019 a midair collision between two helicopters has killed 13 French soldiers fighting against Islamic extremists in Mali. (Christophe Petit Tesson, Pool via AP, File)

BAMAKO, Mali (AP) — Two helicopters collided on a moonless night and killed 13 French soldiers fighting Islamic State group-linked extremists in Mali, France said Tuesday, mourning its highest military death toll in nearly four decades.

The deaths draw new attention to a worrying front in the global fight against extremism, one in which France and local countries have pleaded for more support. In a surge of violence this month, attackers often linked to IS have killed scores of troops in West Africa’s arid Sahel region and ambushed a convoy of employees of a Canadian mining company, leaving at least 38 dead.

French President Emmanuel Macron expressed “deep sadness” after the Monday evening crash. It was France’s highest military toll since 1983, when 58 paratroopers were killed in a truck bombing in Lebanon.

The military said the helicopters were flying very low when they collided and crashed in Mali’s Liptako region near Niger while supporting French commandos on the ground pursuing a group of extremists. No one on board survived.

French defense minister Florence Parly said the helicopters were operating “in the total darkness, which made the operation much more complicated.” The helicopters’ flight data recorders have been found and an investigation has begun.

The French troops were chasing fighters with the Islamic State in the Greater Sahara, affiliated to IS, Army Chief of Staff Gen. Francois Lecointre said.

France’s operation in West and Central Africa is its largest overseas military mission and involves 4,500 personnel. France intervened in Mali in 2013 after extremists seized control of major towns in the north and implemented a harsh version of Islamic law. They were forced back into the desert, where they have regrouped and moved south into more populated areas.

Since 2013, at least 44 French soldiers have died in the mission that has created little public debate in France.

French lawmakers observed a minute of silence on Tuesday. Prime Minister Edouard Philippe defended military operations in the Sahel, saying that “without the ability to face the enemy ... we cannot guarantee, on another hand, the essential work of political stabilization and economic development.”

A new surge in extremist attacks in Mali has killed well over 100 local troops in the past two months, with IS often claiming responsibility. The extremists loot military posts and profit from mining operations while finding refuge in forested border areas. Hundreds of thousands of civilians have fled their homes.

Before his death this year, IS leader Abu Bakr al-Baghdadi congratulated “brothers” in Mali and neighboring Burkina Faso for pledging allegiance.

Public outrage in Mali also has been directed in recent weeks against France, the country’s former colonizer, over the failure to stop the violence that also has led to deadly clashes between wary communities amid suspicions of supporting the extremists.

Mali’s President Ibrahim Boubacar Keita on Tuesday sent his “deepest condolences” to France. “The loss is heavy but the people of the Sahel share your mourning,” he said in a statement.

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Mali’s Liptako region and its Gourma region near the Burkina Faso border have become strategic crossings for extremist groups as they are largely unguarded, the International Institute for Strategic Studies wrote last month. France built a new base in Gossi in the Gourma region this year, it said.

“Despite increased French presence in this zone, military gains remain limited. Both sides barely ever engage in direct confrontation. Militants use guerrilla tactics, rely heavily on improvised explosive devices and hide within the civilian population before and after launching attacks,” it added.

France’s Barkhane military operation is one of multiple efforts against the growing extremist threat in the Sahel including a five-nation regional counterterror force that struggles to secure international funding despite French backing and a peacekeeping mission in Mali that is one of the deadliest in U.N. history.

The United States and others have blocked efforts to set up sustained U.N. funding for the 5,000-strong regional G5 Sahel force.

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Corbet reported from Paris. Associated Press writer Cara Anna in Johannesburg contributed.