BAMAKO, Mali (AP) — The U.N. says five Chadian peacekeepers have been killed and three wounded after they came under attack in northern Mali.

A statement from the U.N. secretary-general's spokesperson says the peacekeepers' convoy hit a roadside bomb and then came under fire from gunmen.

The attack took place Tuesday about 9 miles (15 kilometers) north of Aguelhok in the northern Kidal region. Seven other peacekeepers have been killed there so far this year.

U.N. Secretary -General Ban Ki-moon called it a "heinous attack" and noted it would be considered a war crime under international law.

Islamic extremists have been attacking international peacekeepers and Malian soldiers working to stabilize the north three years after a French-led military campaign ousted jihadis from power.