By Steve Kingstone
BBC correspondent in Sao Paulo
Police are frequently involved in clashes with armed gangs
Police officers in the Brazilian city of Sao Paulo have staged a demonstration demanding better pay and greater resources.
Around 2,000 officers gathered on the city's main thoroughfare to draw attention to what they say are some of the poorest pay and conditions of any police force in the world.
The rally took place amid an unprecedented wave of attacks on police officers which has lasted for more than a week.
The attacks, which have left three officers dead, have been linked to an organised crime gang.
The police are always out in force in the centre of Sao Paulo, but this protest was different.
And now, more than usual, the people of Sao Paulo may have some sympathy.
Over the past eight days there have been more than 40 attacks on police stations and mobile bases.
In addition to the three deaths, 12 others remain seriously injured.
The assailants, who have used machine-guns and grenades, have been linked to an organised crime group known as The First Command of the Capital.
The authorities are interrogating its leaders, who are already behind bars. It is thought they ordered the attacks to protest at prison conditions.
With the arrest of 25 further suspects over the past week, the police insist they can defeat organised crime in Sao Paulo.
But they say they need more resources to do it.