Islamic extremists say they have killed at least 15 people in two attacks in Mali’s northern Kidal region.

Ansar Dine militants said in a website posting Saturday they killed at least 11 Tuareg rebels in an attack Thursday in Kidal. The extremist group said it released prisoners and took weapons. They also claimed another attack Friday in Kidal that killed at least four people.

A Tuareg separatist said the attacks were likely retaliation after separatists killed at least four extremists Dec. 19. He spoke on condition of anonymity because he wasn’t permitted to speak to the press.

Tuareg separatists, then extremists, took Mali’s north in 2012. A French-led operation ousted the extremists in 2013, but attacks continue.

The separatist group signed a peace deal with the government in late June.