Violent attacks have been taking place in the Brazilian state of Sao Paulo in what many see as a full-scale war between the state authorities and the First Command of the Capital (PCC) criminal faction.
Police in Sao Paulo are on alert after a number of attacks
The BBC News website spoke to a number of people living in the state about the violent attacks and the fear they have created.
CRISTIANE NEVES, 26, WORKS IN TOURISM, SAO PAULO CITY
I live in the Santo Amaro neighbourhood in the southern region of Sao Paulo city, where a lot of the violence has been happening.
Things are really out of control now. We are too scared to go outside. I have heard gunshots from my apartment.
Three buses were burnt-out over the weekend and gunmen fired shots into two banks.
I didn't hear of anyone being killed in these attacks. I think they were just for impact.
But many policemen have been killed.
The police are roaming the streets heavily armed.
Many buses have been burnt-out across Sao Paulo
I went out on Saturday and saw police stopping people at gunpoint, which really scared me.
Sao Paulo is not the safest city to live in normally, but now it has really got very bad.
Yesterday the police said that people should go to work as normal today.
But we can't go to work when there are no buses. Many bus stations are closed because the owners of the buses don't want them to be burnt-out.
I am going to stay inside with my family. My friends are doing the same.
I had a job interview this morning but I cancelled it. My dad went to work but we were very worried for him.
I blame the government for its response to all of this.
The PCC warned the government that they would launch attacks 20 days before they did but the government didn't listen.
Now we must stay indoors while all this violence happens outside. The local police chief says it could last for 10 days.
IOLANDA KRUSNAUSKAS, 35, SCHOOLTEACHER, SAO PAULO CITY
I am very afraid at the moment.
Krusnauskas: Criminal use of mobile phones is directing unrest
The government tells us the situation is under control but the violence continues and we're all very scared.
Criminals are burning buses and setting fire to banks.
I live in the north of the city and I can hear fire sirens and police sirens all the time.
I am worried because the local and federal government don't seem to be able to control the violence.
There are not enough police to fight these violent gangs. The police are underpaid and disorganised, whereas the gangs are well organised.
The first step the authorities need to take is to block the prisoners from using mobile phones to direct the violence on the streets.
If you live in Sao Paulo you live in constant fear of being robbed or attacked. This wave of violence has just made that fear worse
I really can't understand how they are allowed to use their phones to pass instructions to criminals outside.
This is what is causing the violence. The prisons are controlled by the prisoners and the government doesn't invest enough to turn the situation around.
We pay high taxes, yet we don't see it being put to use into key areas such as combating crime.
There is also no investment in education, and the two are linked. Invest in education and prisons and we would not be in this situation.
Where is our money going? Into the pockets of a corrupt government I suspect.
Violence like this is more familiar in Rio de Janeiro, not in Sao Paulo.
However, in truth if you live in Sao Paulo you live in constant fear of being robbed or attacked when you walk down the street.
This wave of violence has just made that fear worse.
I am afraid that if it is not controlled now we will have to get used to it in Sao Paulo permanently.
CLAUDIA G, 55, RETIRED, SAO PAULO CITY
People here are very worried and feel panicked because we have never seen anything like this.
I am 65 and have never seen this kind of violence in Sao Paulo.
It has already affected my area, Itaim Bibi, which is in the south-east of Sao Paulo.
One police detective was killed in a restaurant one block away from my house on Friday.
He was shot and killed by two hooded men in front of his wife, according to local reports.
This was a terror attack, in my opinion. But it was not based on religion or ideology, it's simply criminal activity.
It's a very sad situation. We have been told by the local authorities to stay at home.
Although I will have to leave the house to get necessary things such as food, I will listen to what they say and stay indoors as I'm very afraid.
Buses have been attacked with Molotov cocktails and grenades.
There is a heavy police presence and the police are all heavily armed - they are waiting for further attacks.
Many people fear more random attacks and violence and are demanding that the federal government bring in the army to restore law and order.
The state of the penal system in this country is the cause of this violence and the government - local and federal - need to accept some responsibility for that.
EVANDRO PEREIRA, 32, STUDENT, SANTOS, SAO PAULO STATE
There is real worry in the air here.
About 16 people have been killed in areas nearby and about 100 injured by the violence.
The PCC is very strong in this area and there are a lot of prisons.
In Sao Vicente, which is near Santos, there have been riots in three prisons and eight people have been taken hostage, according to local reports here.
I will go to work because I have to but will be very cautious.
The authorities need to gain control of the jails again and we expect them to do so
I will not allow my family to go outside though.
The violence has continued since Friday and is spreading all the time.
I hope that in the coming hours the police will launch their counterattack.
First they need to take all phones from prisoners directing these attacks and arrest the criminals carrying out the attacks on the streets.
It really feels like we are under terrorist attack and we expect a proper response from our government and changes in the law so it does not happen again.
But the government is not saying we are under terrorist attack.
They need to recognise this and address the causes of this violence - such as unfair social conditions and a badly organised criminal justice system.
We are shocked but not fully surprised by this violence. It has been coming for some time. We constantly hear about PCC activities in this area.
The authorities need to gain control of the jails again and we expect them to do so.