The United Nations said three peacekeepers from Chad were killed and four others seriously injured Sunday in attacks against a U.N. convoy in northern Mali using improvised explosive devices.

U.N. spokesman Stephane Dujarric said Secretary-General Antonio Guterres condemned the attacks near Aguelhok in the Kidal region, which may constitute war crimes under international law.

The secretary-general calls on Malian authorities “to spare no effort in identifying the perpetrators of these attacks so that they can be brought to justice swiftly,” Dujarric said.

The secretary-general reaffirms that such cowardly acts will not deter the United Nations from its resolve to continue supporting the people and Government of Mali in their pursuit of peace and stability.

Dujarric said: “The secretary-general reaffirms that such cowardly acts will not deter the United Nations from its resolve to continue supporting the people and Government of Mali in their pursuit of peace and stability.”