Footage from social media shows a police helicopter getting into difficulty after being shot at while flying over a Rio de Janeiro slum known as City of God. The helicopter crashed, killing four officers on board, although it is not yet clear whether the gunfire was the direct cause of the crash </s> Image copyright AP Image caption Firefighters recovered four bodies from the wreckage of the aircraft

Four police officers have died after their helicopter crashed over Rio de Janeiro's notorious City of God favela.

In video footage of the crash, sustained gunfire can be heard before the helicopter drops from the sky, narrowly missing a main road.

The helicopter was giving support to a police operation against gangs in the favela, according to police.

Police reportedly began a large scale operation on Sunday in western Rio, with arrests and seizures of drugs.

'Fell in a ditch'

There had been several clashes during Saturday between police and criminal gangs operating in the City of God favela area.

Firefighters removed the bodies of the victims from the wreckage, which could be seen in the footage crumpled and smoking.

A police spokesman said that forensics officers were examining the wreckage to determine the cause of the crash.

Image copyright Reuters Image caption Police had been carrying out anti-drugs operations on Saturday in the City of God favela

One man who saw the incident, Thiago Duarte, told Associated Press: "We were here watching the shooting in the woods... Suddenly a friend shouted 'the bullets reached the helicopter, it's going to come down!'

"It was clear that [the pilot] was trying to do everything to avoid falling over the shanty town or on the expressway, so it turned back and fell into the ditch."

On Sunday, police backed by an armoured vehicle carried out further operations, with at least two people arrested, another injured and a number of drugs seized.

Rio state security secretary Roberto Sa said police were investigating a territorial dispute between members of two favelas in western Rio.

If the helicopter was shot down by gang members, it would not be a first for the city, which hosted the 2016 Olympics.

In 2009, drug traffickers opened fire on a police helicopter, causing it to explode and crash land on a football pitch, killing both pilots.

Violence has been on the rise in Rio over the past two years following the failure of a 2010 programme to rid the favelas of drug gangs.

A total of 3,649 murders were reported in 2016 up until the end of September, a rise of almost 18% on the same period last year. </s> MEXICO CITY, Sept 6 (Reuters) - Suspected gang members shot down a helicopter in a clash with police in the dangerous western Mexico state of Sinaloa on Tuesday, killing four people, the state's governor said.

Silvano Aureoles, the governor of Michoacan state, said on Twitter that the operation took place near the violent city of Apatzingan, and was aimed at detaining "leaders of criminal cells". It was not immediately which gang was responsible.

"During the operation, an official helicopter which was supporting the patrol in area of difficult access was shot down," he said. "We lament the death of the pilot, three police officers and a police officer who was injured." (Reporting by Gabriel Stargardter, Adriana Barrera and Lizbeth Diaz; Editing by Simon Gardner)
Four policemen are killed in Brazil after their helicopter is shot down by a "gang".