(SomaliNet) In the fourth hand grenade in just a week, four people were killed and 20 others severely wounded in the Burundian capital, authorities said on Monday, Reuters reported. The catastrophic incident left two people dead on the spot and two others died in the hospital. According to a local official, the attacks were carried out by unknown assailants on Sunday night in the northern Bujumbura suburb of Ngagara. "Those criminals threw five grenades and shot at customers who were drinking beer," local government official Aime Desire Ndibanje said. But no arrests were made so far and police had no immediate suspects. Meanwhile, some 300,000 illegal guns are thought by the Burundian government to be in the hands of civilians and armed groups.