Three people have been arrested after a teenager was stabbed near a park.
The Metropolitan Police said officers were called to North Street in Barking, east London, at 7.24pm on Monday following reports of a stabbing.
Police and the London Ambulance Service rushed to the scene, near Barking Abbey Grounds, where they found a male, believed to be 17, suffering from a stab wound.
The teenager was taken to hospital, where his condition is believed to be life-threatening, the Met added.
One witness told the PA news agency that three people in hoodies had been seen fleeing the scene in a car moments after the attack.
The woman, who wished to remain anonymous, said the teenage victim was a black male who is believed to live locally.
She added: “There was a group of youths around here, then three of them ran across the road and, literally 30 seconds later, ran back and jumped in a car.
“The police turned up, there was a young lad on the floor. They had stabbed him in the stomach.
“Then they had the blatant cheek to come back and watch. They literally walked over and stood there, seeing the people working on this kid.
“Then they walked back and got back in car, laughing their heads off.
“That was what shocked me more – that they had the cheek to come back.”
The witness said the youths were black, were wearing dark clothes and hoodies, and she believed they were in their late teens.
She added: “They were sort of 16- to 18-year-olds. They were all dressed in hoodies, all in black.”
One shop worker said he had closed the store in nearby East Street at 8pm to find police with dogs searching the area.
The man, who wished to remain anonymous, added: “We don’t know when the police came but when we closed we saw the tape.
“They had dogs and everything in the roads and were checking the area.”
A police cordon manned by uniformed officers was in place around a large area of the park between St Joseph’s Primary School and St Margaret’s Church on Tuesday morning.
Barking Parish Church – St Margaret posted on Facebook: “Owing to an ongoing police investigation, St Margaret’s Church and Centre will remain closed for the day.
“Our thoughts and prayers are with both the young man who was the victim of a knife attack last night, and his family and friends.”
Three people have been arrested in connection with the incident and remain in custody, the force said.
Inquiries continue to establish the full circumstances surrounding the stabbing, Scotland Yard added.
Witnesses should call the police on 101, quoting ref 6440/11nov.