UNKNOWN assailants set off four grenades in Burundi's capital Bujumbura yesterday, killing two people and wounding several others, police said. One victim died instantly when the grenades went off in three different places as dusk fell, while one assailant was arrested after being wounded by his own grenade. They were the first such explosions in the city since President Evariste Ndayishimiye took office last June, though eight people were killed on May 9 in Muramvya province, about 65 kilometres (40 miles) away when unknown gunmen ambushed several cars. Ndayishimiye, who took office on his predecessor Pierre Nkurunziza's death, has carried…