In Tanzania, at least six children have been killed and 25 others injured in an explosion at a primary school in north-west part of the country. Reports say, the pupils were playing with a grenade they had found. <br/><br/>Three were pronounced dead at the time they arrived at hospital. The others succumbed to their wounds. The school is in Kagera region near the border with Burundi. The BBC's Leonard Mubali in Tanzania reports that the region hosts refugees from neighbouring Burundi, some of them ex-soldiers, who could have abandoned their weapons in the area.<br/><br/>