New York police would not confirm reports that officer who 'stood by' as the assault took place was under investigation

A road rage attack by bikers that left a New York motorist injured was witnessed by at least one undercover police officer riding with them who did not intervene and then waited three days before reporting his presence, it was claimed on Saturday.

Alexian Lien was the driver of a black Range Rover that was pursued and attacked by a number of motorcyclists last weekend, after he bumped one of them with his vehicle and then ran over another, leaving the man critically injured. The chase was captured on another biker's helmet-mounted camera.

New York police said on Saturday that two suspects in the attack on Lien had turned themselves in, but would not confirm reports that the NYPD's internal affairs division was investigating an officer who allegedly joined in the chase but stood by as the assault took place.

Anonymous law enforcement sources told the New York Post, however, that the officer has been placed on limited duty and had surrendered his gun and police badge while the unit looked into his story.

Lien, who was driving with his wife and two-year-old daughter, was dragged from the vehicle and attacked, leaving him with a slashed face and other injuries.

"It does not appear [the officer] got involved in the scene. He didn't want to blow his cover," the source said, adding that the officer had hired a lawyer to represent him. The New York Daily News reported on Saturday that at least two undercover detectives were riding with the gang.

Much of the pursuit, along the Henry Hudson Parkway in Upper Manhattan, was captured by another biker's helmet-cam, but the video cuts out shortly after the Range Rover comes to a stop with flat tyres and two riders are seen smashing the vehicle's windows with their helmets.

An NYPD spokesman said on Saturday that Robert Sims, 35, of Brooklyn, turned himself in on Friday and was charged with gang assault and criminal possession of a weapon, among other offences. Reginald Chance, 38, also of Brooklyn, also surrendered on Friday and charges were pending, the spokesman said. Christopher Cruz, 28, of Passaic, New Jersey, was charged earlier in the week with reckless driving, for allegedly slowing his motorcycle in front of Lien's vehicle, causing it to be bumped.

The family of Edwin "Jay" Mieses, the rider run over by Lien, 33, as he sped away from a group of bikers that surrounded his car, said he remained in hospital in critical condition. Gloria Allred, the celebrity lawyer hired by Mieses' relatives, appeared at a press conference in New York to claim Mieses would probably be permanently paralysed from the waist down, after his spine was crushed. She said he was an innocent victim who also suffered broken ribs and legs.

"He told everyone to move on and go back to riding. His sole intention was to defuse the situation," she said. "Watch that huge vehicle, SUV, blast off, and watch it as it is lifted several feet off the ground as it rolls over Edwin Mieses."

Mieses' family and supporters have called for Lien to be prosecuted.

Forensics experts were examining the Range Rover on Saturday at a police precinct in Washington Heights, where the chase ended. Photographs showed the vehicle with its front and tailgate windows smashed and with three flat tyres.

On Thursday, Rosalind Ng, Lien's wife, released a statement claiming that it was "a life-threatening situation" and that her husband had no choice but to drive off when angry bikers surrounded their vehicle.

"We know in our hearts that we could not have done anything differently," she said, adding that the family was "placed in grave danger by a mob of reckless and violent motorcyclists".