Story highlights French troops conduct an operation in northern Mali, coordinating with Malian forces

They kill Ahmed el Tilemsi, co-founder of the Movement for Unity and Jihad in West Africa

A French official says a dozen other militants were with el Tilemsi when he was killed

The U.S. had designated el Tilemsi a terrorist, offered a reward of up to $5 million for him

French troops killed a senior jihadist leader in northern Mali -- a man purportedly behind a number of high-profile attacks and kidnappings, and ambitious and brazen enough that the United States had issued a $5 million reward for him -- the French military announced Thursday.

Ahmed el Tilemsi was the military head and co-founder of a jihadist group called the Movement for Unity and Jihad in West Africa, one of several jihadist groups active in the region.

The U.S. government designated el Tilemsi a terrorist in December 2012 and offered a reward of up to $5 million for information leading to him.

He was killed Wednesday night in a French military operation, which was coordinated with Malian forces, in the Gao region in Mali, French military officials said.

"One of the things that proves he was a senior chief (in the group) is that when he got killed ... he was accompanied by a dozen (fighters) who were also ensuring his security," French Defense Ministry spokesman Sacha Mandel said.

About 10 suspected terrorists were "neutralized" -- which means killed or taken captive, according to the French military -- in the same operation, said Col. Gilles Jaron, another French military spokesman. Mali is a former French colony.

According to the U.S. State Department, el Tilemsi was among the militants who in September 2011 broke off from al Qaeda in the Islamic Maghreb -- another terrorist group -- to form the Movement for Unity and Jihad in West Africa.

A month later, the group, also known as MUJWA, abducted three aid workers from a refugee camp in western Algeria. The U.S. government blames the Movement for Unity and Jihad in West Africa for an attack on a police base in Tamanrasset, Algeria, and another in Ouargla, Algeria, as well as the kidnapping of seven Algerian diplomats -- incidents that all occurred in 2012.

The State Department described el Tilemsi, a Malian born in 1977, as MUJWA's military chief, adding that he directly took part in the October 2011 kidnappings in western Algeria.

Before that, as a member of al Qaeda in the Islamic Maghreb, he took part in the abduction of two French nationals in the Niger city of Niamey, the U.S. government said.