The United Nations says the death toll in an attack on UN peacekeepers in the Democratic Republic of Congo has climbed to 15, and the UN will fly its flags at half-staff Monday in tribute. <br/><br/>The peacekeepers, all from Tanzania, were working at a UN mission in DRC's troubled North Kivu province, home to the Ugandan rebel group the Allied Democratic forces (ADF). <br/><br/>A UN official said that the group, which has attacked the mission in the past month, is suspected to be behind Thursday's attack. Reports say at least two more peacekeepers are missing. <br/><br/>The UN mission, MONUSCO, said at least five Congolese soldiers were also killed in the protracted fighting between suspected ADF elements and MONUSCO and Congolese forces.<br/><br/>Tanzanian President John Magufuli has expressed shock over the attack. At the United Nations on Friday, the UN Security Council held a moment of silence for the victims, followed by closed consultations on how to respond. <br/><br/>UN Secretary-General Antonio Guterres has called the attack a war crime. Guterres expressed his "outrage" after Thursday's attack, which also left about 40 people injured.