Some 9,000 officers across the country are taking part in the action, Brazil's Globo television reported.

The police union say they have only had 50% of a wage rise agreed last year. The second rise was due in January.

The police are carrying out only some essential duties, such as attending emergencies and covering jail security.

There were reports of problems at Brazil's international airports because of a lack of police officers on duty.

But the situation has returned to normal, following an appeal from Brazil's justice ministry, Globo reported.

In a separate development, Brazil's central bank employees are also holding a 24-hour strike over pay conditions.