Violent attacks in Sao Paulo

Over 50 people, including police officers, have been killed following a wave of violence by heavily armed gangsters in Brazil's Sao Paulo.

A criminal gang is thought to be behind more than 100 attacks on police stations, patrol cars and bars popular with off-duty officers, with machine guns, machetes and home-made bombs.

Commentators are claiming that the violence marks a declaration of war by the First Capital Command gang (PCC) on the Sao Paulo authorities.

Enio Lucciola, a spokesman for the state's public safety department, called the attacks "the most vicious and deadliest attacks on public security forces that have ever taken place in Brazil".

The uprisings began on Friday after 765 prisoners were transferred to a maximum security unit and continued throughout the weekend.

Over 200 prison guards are being held hostage in over 40 state prisons, as officers struggle to control the violence.