A wave of attacks on police by a notorious gang has killed at least 30 people - including 23 officers – in the bloodiest assault of its kind in the history of Brazil’s largest state, authorities said.

Eight prisoners have died in a collapsed tunnel and 32 others are still at large after one of the most daring escape attempts in recent memory from the sprawling Sao Paulo State Penitentiary in Brazil.

Prisoners in Brazil are due to meet ministers after they threatened more rioting when officials banned visits during the Carnival holiday.