A United nations peacekeeper was killed and four others wounded Sunday in northeastern Mali

A United nations peacekeeper was killed and four others wounded Sunday in northeastern Mali, when their vehicle hit a roadside bomb.

A U.N. statement said the blast occurred in the Kidal region and that all of the victims were from Chad. 

U.N. Secretary-General Ban Ki-moon, in a statement, stressed that attacks targeting U.N. peacekeepers may constitute war crimes under international law.  He also said that attacks on regional peacekeepers "will not weaken the determination of the mission to fully implement its mandate" to monitor a peace deal reached after Islamists sought to seize control of northern Mali in 2012.

A French military intervention later quelled the crisis, clearing the way for U.N. peacekeepers who deployed in July 2013.  The mission has since been regularly targeted by Islamists, with a death toll compiled by the French news agency showing 28 people killed so far this year.

The U.N. Security Council earlier this year boosted its peacekeeping force to 15,200 troops and police in the country.