Nine United Nations peacekeepers in Mali were killed in an ambush on their convoy yesterday, the deadliest attack on the U.N.

mission in Mali yet, a spokesman for the mission said.

The peacekeepers, from Niger, came under attack from unidentified, heavily armed gunmen on motorbikes between the northeastern towns of Menaka and Ansongo.

"I am horrified by this cowardly act of terrorism," Arnauld Akodjenou, deputy head of the U.N. mission, known as MINUSMA, said in a statement. U.N. peacekeepers have deployed across Mali's north in an effort to secure the vast desert zone that was occupied by a mix of al Qaeda-linked Islamists in 2012 until the insurgents were scattered by French forces last year.

The presence of international troops allowed Mali to hold elections last summer but there has been a spike in attacks by Islamists in recent months.