The blast hit the peacekeepers while they were out on a morning run in the western Goma neighbourhood of Keyshero, the mission added. The cause was not immediately clear. Ismael Salumu, an imam at a nearby mosque, said three peacekeepers were killed. 'We just heard the explosion and the cries. We then ran over to see,' he told Reuters. About 18,000 uniformed UN personnel operate in Congo, where millions died in regional conflicts between 1996-2003 and dozens of armed groups continue to operate.