Sao Paulo: At least 25 inmates died Sunday in clashes between two rival factions in a prison in far northern Brazil, local media reported citing police.

Among the dead, seven were beheaded and six burned to death in fighting at a prison in Boa Vista, the capital of Roraima state, the news site G1 reported, citing local police.

The riot occurred during visiting hours and about 100 relatives of prisoners were detained for several hours before being released by police, EFE news reported.