Antonio Taylor, 31, allegedly 'ambushed' and shot a police officer during a traffic stop in Missouri

A police officer has been critically injured after he was 'ambushed' and shot during a traffic stop in Missouri.

The white officer, who has not been named, was fired at three times by 31-year-old black man Antonio Taylor, police in St Louis said.

The cop had his back turned when Taylor 'advanced quickly' from behind, leaving him 'completely helpless', St Louis County Police Chief Jon Belmar said.

It is not clear if the attack has any connection to the shooting of 12 police officers in Dallas on Thursday, in which five cops died, but Taylor is not believed to have any link to the officer.

The cop was walking back to his car after pulling over the motorist when he was attacked, Ballwin Police Chief Kevin Scott said.

The officer was going to check the driver's details when the suspect got out of the vehicle and fired three times, the police chief said.

The officer 'had no chance at all' to pull his handgun and 'was completely helpless,' Scott added, noting that the incident was recorded by the police car's dashcam.

Taylor allegedly sped away after the shooting and was arrested four miles away after his car was spotted by an officer from a neighboring police department.

The motorist allegedly tried to flee but was caught after a five-minute chase.

'Make no mistake: We believe during this investigation that Ballwin officer was ambushed, period,' Belmar said.

St Louis County Prosecutor Bob McCulloch said there was no evidence of any dispute between Taylor and the officer before the gunfire.

The cop had his back turned when Taylor 'advanced quickly' from behind, leaving him 'completely helpless', St Louis County Police Chief Jon Belmar said. Pictured, police at the scene

The cop was walking back to his car after pulling over the motorist when he was attacked, Ballwin Police Chief Kevin Scott said. Pictured, police at the scene

Scott said he 'can't even begin to speculate' about a motive, including whether the shooting involving the white officer, a nine-year police veteran, had racial overtones.

He added that Taylor was on probation for stealing a car in Oklahoma and has previously served prison time for illegally possessing a firearm. He was paroled in March last year.

Taylor has been charged with assaulting a police officer, armed criminal action and illegally possessing a firearm.

McCulloch said there's no evidence of any dispute between Taylor and the officer before the gunfire.

The shooting on Friday morning came less than 12 hours after veteran Micah Xavier Johnson shot 12 police officers and two civilians in Dallas, killing two cops.

There was outrage on Wednesday after black man Philando Castile was shot dead by a police officer during a traffic stop. His girlfriend live streamed his death on Facebook.