Two men have been arrested after three men were stabbed to death in east London.
Police said a fight broke out between two groups from the Sikh community armed with knives in Seven Kings, Ilford, on Sunday evening.
All three men were pronounced dead at the scene. Two men, aged 29 and 39, have been arrested on suspicion of murder, the Metropolitan Police said.
Police said the victims of the latest knife crime attack in London are believed to be aged in their 20s or 30s.
Officers were called to Elmstead Road at about 7.40pm on Sunday.
Speaking at the scene on Monday, Chief Superintendent Stephen Clayman said the suspects and the victims were all known to each other.
"We believe the groups involved are members of the Sikh community," he said.
"A fight has taken place which has escalated, resulting in three people being fatally attacked."
Officers are still contacting members of the dead men's families, he said.
"It was a horrific scene for anyone to come across and my heart goes out to the families and those affected by it because it is unprecedented to have something like this," he said.
While police are still investigating a motive, they have ruled out terrorism, he said.
A police cordon was in place outside Seven Kings railway station on Monday morning.
Scaffolder Louis O'Donoghoe, 40, was watching snooker on television when he heard screaming and shouting outside his house, in what he said sounded like a foreign language.
"It was just chaos, absolute chaos. It was like something out of a movie, horrific," Mr O'Donoghoe, who is originally from Middlesbrough, said of the aftermath.
He saw the ambulance service working on one person, and then realised there were another two bodies, at which point he went outside to see what was going on.
"I could see it all, one (body) to the left, two at the bottom of the stairs. It was like a bad day in Bosnia. It was pretty horrific really. I've never seen anything like it to be honest. It's like something on a movie."
The owner of Seven Kings Cars opposite the station said a man with blood on his hands had approached him on Sunday evening asking for help after three people had been badly injured.
Nadeem Rana told the PA news agency: "I was shocked. He had blood on his hands and he said there were people in very poor condition."
The man and a passenger who had been waiting for a taxi made off towards the scene to help, Mr Rana said.
He said he was shocked to hear the men had died.
"It's shocking, a feeling of insecurity to be honest," he said.
Local resident Lauren Marshall said she and other neighbours had gone out into Elmstead Road when they saw flashing police lights on Sunday night.
"By the time I came out, the road was blocked and there were police everywhere. It was manic. Everyone was coming out of their houses," the 26-year-old paralegal told PA.
"I've lived here my whole life and nothing like this has ever happened. It was a shock."
Jas Athwal, leader of Redbridge Council, said he believes knives were used in the bloody killings and that it was an isolated incident.
"An incident like this is unheard of within the Sikh community here in Redbridge," he said.
"I think tragically there are at least three families who are going to be in mourning and this is going to last a lifetime for the people left behind.
"We've got to look at the causes of why this happened and address those."
The London Ambulance Service said they had a report of a stabbing outside of Seven Kings station.
A spokesman said: "We sent a number of resources including three ambulances, three medics in response cars, two critical care paramedics, two incident response officers and our hazardous areas response team. We also dispatched London's Air Ambulance.
"Sadly, despite the efforts of medics, three males were pronounced dead at the scene."
Extra police enforcement powers have been authorised for the whole of Redbridge borough until 8am tomorrow.— Sadiq Khan (@SadiqKhan) January 19, 2020
Please contact the police on 101 or contact @CrimestoppersUK anonymously if you have any information.
London mayor Sadiq Khan tweeted that extra police enforcement powers have been authorised for the whole of Redbridge borough until Monday at 8am.
Formal identification of the victims has yet to take place, and post-mortem examinations have also yet to be arranged.
So far in 2020 there have been six murders in the capital. Last year there were 149, a rise from 133 in 2018, despite a drop nationally.