Four people have been killed and six others injured in a mass shooting at a backyard party in California during a Sunday night football game.

Police said a gunman or multiple gunmen snuck into the backyard and opened fire at a home in Fresno where dozens of people were watching a game on Sunday at about 6pm.

Three people were found dead in the backyard of the home and a fourth died in hospital.

Six others are being treated in hospital for gunshot wounds but are expected to survive.

All of the victims were Asian men between 25 and 35 years old.

The unidentified suspects fled the scene and police are now combing the neighborhood for witnesses and surveillance footage.

Four people were killed and six others injured in a mass shooting at a backyard party in Fresno, California during a Sunday night football game

People console each other near the scene of Sunday night's shooting in Fresno where a gunman or gunmen snuck into a backyard and opened fire

Fresno police Lt Bill Dooley said the 'mass shooting casualty' took place at around 6pm local time on the 5300 block of East Lamona Avenue

Three people were found dead at the scene and a fourth died in hospital. All of the victims were Asian men between 25 and 35 years old

Fresno shooting is latest in wave of California gun violence California has been rocked by a series of mass shootings in recent weeks. Last Thursday, 16-year-old gunman Nathaniel Berhow shot five students at his high school in Santa Clarita, killing two. He shot himself in the head with his .45-caliber handgun and died the next day. Thousands of people attended a vigil for the victims last night. The motive is still unclear, and Berhow has not been linked to any terrorist group or extreme ideology. On Saturday, a man shot dead his wife and three of their children in San Diego before killing himself, with a fourth child on life support. Investigators say the parents were estranged and the mother had obtained a restraining order against the father. Reports said police had gone to the house two weeks ago to 'keep the peace' when the man came over to retrieve tools. Last month there were two mass shootings at Halloween parties, leaving eight people dead in Long Beach and Orinda. Members of rival gangs from San Francisco and Marin City were among those at the Orinda party, it is believed. The shooting took place at an Airbnb home, prompting the rental website to promise new measures to stop unauthorized parties. According to the Gun Violence Archive, there have been more than 40 mass shootings in California in 2019. There have been 370 in the United States this year, the organization says. Advertisement

Detectives believe the shooting was 'very likely targeted' but say the motive is unclear.

'Somebody picked that house and came up and shot several times at the backside of it. It looks like there was a target, but we just don't know what the reason for the targeting was,' deputy police chief Michael Reid told reporters.

There was no immediate indication that the victims knew their killers. Police also said there was no history of calls for law enforcement at that home.

Police Lt Bill Dooley said the 'mass shooting casualty' took place at around 6pm local time on the 5300 block of East Lamona Avenue.

Around 45 family and friends - some of them wearing football jerseys - had gathered to watch the game, including some children.

Police said the women and children appeared to be inside the home when they shooting unfolded.

Neighbors told the Fresno Bee that they had heard as many as 10 rapid-fire gunshots on Sunday night.

'Officers arrived on scene – what we found were several individuals deceased in the backyard,' Dooley said at the scene.

Authorities have not released information on the shooter or shooters and no suspect was in custody as of late Sunday night.

'What we do know is that this was a gathering, a family and friend gathering in the backyard,' Dooley said.

'Everyone was watching football this evening when unknown suspects approached the residence, snuck into the backyard and opened fire.

'The initial information is that somebody came up on foot, at least one suspect, and began firing.

'They fired into the backyard where most of the people were in this party, striking 10 people in the course of that gunshot.'

'Our heart goes out to the families of the victims... this is senseless violence.

'We are doing everything we can to bring the perpetrators to justice.

'Thank God that no kids were hurt,' he said.

Six others are being treated in hospital for gunshot wounds but are expected to survive

Detectives believe the shooting was 'very likely targeted' but say the motive is unclear. There was no immediate indication that the victims knew their killers

Around 45 family and friends - some of them wearing football jerseys - had gathered to watch the game, including some children, when the shooting unfolded

Emergency vehicles on the scene in Fresno, California where at least four people were killed in a mass shooting last night

Police and emergency personnel on the scene of a shooting at a backyard party in Fresno

Fresno Police Deputy Chief Michael Reid (center) confirmed in a 10pm update that ten people had been shot. Three died at the scene and one in hospital

Reid said it was unclear how many perpetrators had been involved in the shooting and said there was no initial indication that the incident was gang-related.

Fresno prosecutor Andrew Janz said the shooting was 'still under investigation', adding: 'Rest assured we will bring those responsible to justice.'

'We are praying for peace and calm as we continue to investigate. My thoughts are with the victims and their families,' he said.

California state senator Andreas Borgeas said: 'I am saddened by the disturbing and senseless act of violence tonight in Southeast Fresno.

'My heart is with the family and their loved ones. Thank you to all those who are reaching out in support of Fresno during this time.'

There was a heavy police presence in the road of single-story homes and part of East Lamona Avenue was cordoned off overnight on Sunday.

Police at the scene in California late last night after the gunman or gunmen fled the scene

Police work at the crime scene after a shooting in Fresno in which at least four people died

Vehicles are parked outside a house in the street where the shooting occurred on Sunday night

Police were going door-to-door in search of surveillance video that might help them track down the suspects. The shooting took place about a half-mile from the city's airport.

Agents from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives field office in San Francisco also responded to the shooting.

Authorities have asked anyone with information about the shooting to call Fresno PD at 559-621-7000.

It was at least the second fatal gun attack Sunday in southeast Fresno. A man in his 20s was shot to death early Sunday at a home in another part of the city. Police have not said whether the incidents could be connected.

Choua Vang, who lives near the site of the attack, told the Fresno Bee that the shootings 'make me feel unsafe to be outside when the sun's down'.

On Thursday, a 16-year-old student at a Santa Clarita high school shot and killed two classmates and wounded three other teenagers before shooting himself in the head. He died the next day.

Police in San Diego said a husband shot and killed his wife and three of their sons before killing himself on Saturday. A fourth son wounded in the shooting was on life support on Sunday, family members said.

There was a heavy police presence in the road of single-story homes and part of East Lamona Avenue was cordoned off last night

Lt Bill Dooley (pictured) said about 45 people were at the party when shots rang out

Several police cars and ambulances are at Lamona Avenue near Sandau Avenue for reports of a possible shooting. Several police cars and ambulances are at Lamona Avenue near Sandau Avenue in Fresno for reports of a possible shooting. Posted by FOX26 on Sunday, 17 November 2019