Police in the Brazilian city of Rio de Janeiro have resumed a controversial security operation, following a weekend of violence.
Police are frequently involved in clashes with armed gangs
Sixteen people, including three police officers, were killed in some of the city's poorest neighbourhoods.
On Monday the state authorities announced that 850 officers would be sent out to target drug gangs.
Known as Operation Maximum Pressure, this uncompromising style of policing was first launched in November.
It was then suspended during last month's Carnival.
It involves teams of armed police officers launching surprise raids in Rio's shantytowns, or favelas, with the aim of arresting alleged drug dealers.
The policy has been revived following one of the most violent weekends in recent memory.
The 16 people killed included three police officers. Two were shot while on patrol.
The other was killed in a bar in front of his wife.
Human rights groups have warned that the new tactics will only fuel mistrust between the police and local communities.
Last year, officers killed more than 1,000 people in the state of Rio de Janeiro.
Often they have been accused of shooting first and asking questions later.
But the state government says Operation Maximum Pressure has achieved results.
In the three months from November it produced nearly 600 arrests. During the same period officers seized 400 illegal guns.