By Gary Duffy
BBC News, Rio de Janeiro
The police in Rio de Janeiro are engaged in a war on drugs that the authorities are determined they should not lose.
Slum dwellers live on the frontline between the police and gangs
In a single confrontation this week in one group of favelas, or slums, known as the German complex, at least 19 people were killed.
It was one of the biggest police operations of its kind, involving around 1300 officers. The death toll is expected to rise.
The German complex has been surrounded by police since 2 May, after two police officers were killed.
The strategy has been to contain the movement of drugs and arms.
In what amounts to a siege, around 40 people in total have been killed and more than 60 injured.
The police strategy of taking the fight directly to the areas where the drug gangs operate is controversial, but there is no sign yet of it coming to end.
Over 100,000 people live in the German Complex and there is nowhere for them to go while this conflict continues.
Schools and shops have often had to close, and daily life can often involve taking cover while the police and gangs exchange shots with high calibre weapons.
In one recent exchange, a man was killed at a petrol stage by a shot fired up to two kilometres away.
Rio has around 750 favelas, home to over one-and-a-half-million people, and around 360 of those are believed by the authorities to be under the influence or control of powerful drug gangs.
Rio's governor, Sergio Cabral, who took office earlier this year, says he is determined to change that situation.
"Of course it is worthwhile to fight the drug dealers, but not for the innocent people die. But it is right to fight the dealers. We don't have another way."
"It's not worth seeing an innocent person killed by a stray bullet and many times the stray bullet is fired by an evil drug dealer to turn the community against the police."
Julita Lemgruber, director of the centre of studies of security and citizenship at the University of Candido Mendes in Rio, is one critic of the current strategy.
"I think they are treating the German complex as a pilot project," she says.
"They want to show it is possible to confront the drug dealers and get them out of there, but there is nothing on the horizon to show they are going to do that.
"And they would have to think of all the other favelas where they would have to have the same strategy. They just don't have enough people to do that," she says.
Living in fear
As always it is the ordinary people who are suffering most in this conflict.
We spoke to Maria, whose six-year-old daughter was shot dead some years ago, and who herself been hurt in a shooting by the police.
The interview took place inside a community centre in the favela of Vila Cruzeiro, but even then we had to stop briefly as shots rang out nearby.
Maria is traumatised by what has happened to her but is too poor to move anywhere else.
"I lost my daughter 10 years ago because of a stray bullet in a conflict between police and drug dealers.
"At the start of this operation I was shot by police, and they shouted in the community that anyone taken to the hospital would be finished off there."
"I am frightened. My other daughter has asked what she will do if I am killed."
Pan American games
Police seized a wide range of weapons, drugs and explosives in the latest raids in the German complex.
They say that all those killed were suspected drug dealers.
But the community at the heart of this conflict is angry and frightened.
Rio will soon play host to a major sporting event - the Pan American games, attracting 5,000 athletes and tens of thousands of tourists.
Security will be tight but the authorities deny the latest operation is linked to that event.
They say they simply waited until they had enough intelligence before the raid took place. The operation they say was courageous.
But it is clear that Rio's war on drugs is far from over.