PARIS (Reuters) - The French military has targeted Islamist militants in northern Mali near the border with Algeria and took 15 militants “out of action”, an armed forces spokesman said on Thursday.

It was not immediately clear if the operation had any connection to the pursuit of assailants who killed four U.S. soldiers in an ambush on Oct. 4 in western Niger, about 400 kilometres to the south.

The French operation in the region of Abeibara took place overnight on Monday and targeted members of Islamist militant group Ansar Dine, the spokesman said.

It involved French Mirage jets, attack helicopters and forces on the ground, he added without providing details on how many of the 15 militants targeted had been killed or wounded.

France intervened in Mali to ward off an offensive by Islamist militants that began in 2012. Around 4,000 of its troops remain in the region as part of Operation Barkhane, where they work alongside around 10,000 U.N. peacekeepers in Mali.

The U.S. deaths have drawn attention to counter-terror efforts in the arid Sahel region where an Islamist insurgency involving countless armed groups has been intensifying for years, regularly killing local soldiers.