By Mohammed Ghobari SANAA (Reuters) - Shi'ite and Sunni Muslims fighters agreed to a ceasefire on Monday after days of clashes in a northern Yemeni town in which at least 100 combatants and civilians were killed. A Red Cross delegation had managed to enter the town of Damaj to treat and evacuate those wounded in the fighting, but a translator with the team was shot and killed, he said. The ceasefire was announced by the U.N. envoy to Yemen, Jamal Benomar, according to the state news agency. Sectarian rivalry between Sunni Salafists and Shi'ite Houthis in Damaj has cast a shadow over reconciliation efforts in Yemen, a neighbor of oil exporter Saudi Arabia and home to one of al Qaeda's most active wings.