Thousands farewell to murdered NY officer

Thousands of mourners have gathered in a Long Island town to bid farewell to a New York police officer who was shot in the head by an alleged career criminal.

Brian Moore, 25, was the third New York officer killed in America's biggest city since December against a backdrop of nationwide protests and racial tensions over police killings of unarmed black suspects.

Moore, who was in plain clothes, was shot in the head while inside his unmarked car with another police officer in the borough of Queens last Saturday. He died in hospital two days later.

New York Mayor Bill de Blasio and police commissioner Bill Bratton were to lead the mourners at the funeral.

"It's awful, frightening reminder of the sacrifice that so many men and women in law enforcement make. More and more it's obvious the danger of the job," New York Governor Andrew Cuomo said on Friday.

Demetrius Blackwell, 35, an ex-convict and a career criminal, was arrested shortly after the shooting and faces murder charges over Moore's death.

He allegedly opened fire on the officers as they tried to follow him.