United Nations Secretary-General Antonio Guterres said he was extremely concerned over the fresh resumption of hostilities between Armenia and Azerbaijan in the breakaway region of Nagorny Karabakh. “The Secretary-General strongly calls on the sides to immediately stop fighting, de-escalate tensions and return to meaningful negotiations without delay,” Guterres’s spokesman said in a statement. Arch foes Armenia and Azerbaijan have accused each other of initiating clashes on Sunday that claimed at least 23 lives and threatened to draw in regional powers Russia and Turkey. The worst clashes since 2016 have raised the specter of a fresh war in the decades-long territorial dispute over Nagorny Karabakh. Sixteen Armenian separatist fighters were killed and more than 100 wounded in the fighting. Both sides also reported civilian casualties. Guterres “condemns the use of force and regrets the loss of life and the toll on the civilian population,” the statement said, adding that the secretary-general would speak to the president of Azerbaijan and the prime minister of Armenia. France, Germany, Italy and the European Union also urged an immediate ceasefire. The United States has condemned escalating violence, calling on both sides to cease hostilities immediately. The State Department said in a statement that both sides should immediately end the violence, as well as any rhetoric or other actions that could worsen tensions. It said any participation in the escalating violence by outside parties would be “deeply unhelpful”.