An American police officer has been shot and killed while transporting a prisoner to a jail in New Orleans, officials say.

Police officer Daryle Holloway was shot in his patrol car while driving 33-year-old Travis Boys to Orleans Parish Prison on Saturday morning.

Holloway, 45, a husband and father of three, was pronounced dead at a New Orleans hospital.

The suspect, who had been arrested hours earlier on suspicion of aggravated assault, allegedly smuggled a gun into the vehicle. After managing to free himself from handcuffs, Boys grabbed the gun, got into the front seat through a gap in the cage, which separates the front and back seats of the police car, and shot Holloway as he was driving , the New Orleans police said.

When Holloway was shot, his car crashed into a utility pole near a Shell gas station and Boys escaped on foot.

"According to the initial investigation, Boys shot Officer Holloway from within the vehicle during the transport. After the vehicle crashed, Boys fled the scene," police said in a statement.

"Today is an extremely sad day," said Police Superintendent Michael Harrison. "Not only is it a sad day for me, it's a sad day for the city of New Orleans, especially the Holloway family."

He said the police would launch “a large manhunt” to find and arrest the suspect.

Also, Mayor Mitch Landrieu released a statement, saying that a team of law enforcement officers would conduct the manhunt “to find, capture and prosecute the person for this heinous crime."

SB/AT