Bill de Blasio (L) has been supported by New York police commissioner William Bratton (C). Photo: AP

Bill de Blasio said the public snubbing had been disrespectful to the families of the two men and to the city.

Officers Wenjian Liu and Rafael Ramos were shot dead last month by a gunman with a grievance against the police.

Many police have resented the mayor's expressions of sympathy for anti-police protesters in recent months.

"Those individuals who took certain actions the last two weeks, they were disrespectful to the families involved. That's the bottom line," Mr de Blasio told reporters at police headquarters.

"They were disrespectful to the families who lost their loved ones. I can't understand why anyone would do such a thing in the context like that."

Mr de Blasio also dismissed suggestions that police had been working to rule since the killing of the two officers.

He described the apparent fall-off in arrests and court appearances for minor offences as an aberration.

"I certainly don't think a few very aberrant days suggest anything compared to what you see over the course of the whole year," he said.

Mr de Blasio's remarks were supported by New York's police commissioner, William Bratton, who said that the officers who turned their backs on him had "embarrassed themselves".

"The idea of what is effectively a labour action being taken in the middle of a funeral where we are honouring the death of two police officers - I just don't understand it," Mr Bratton said.

Speaking after the policemen were shot, the head of the city's largest police union, Patrick Lynch, hit out at the liberal mayor, saying there was "blood on many hands".

The shootings followed a wave of demonstrations over killings of unarmed black men by white police officers, beginning in the Missouri town of Ferguson last summer.

There was anger in New York after a grand jury decided not to press charges against a white police officer over the death of unarmed black man Eric Garner, who was placed in a chokehold while being restrained by police officers.

Mr de Blasio had expressed solidarity with the protesters and had publicly wondered if his son, who is mixed-race, was safe from police.

Critics have argued that such rhetoric helped to create an environment that encouraged violence against police.

The man who shot the two officers - Ismaaiyl Brinsley - killed himself in a subway station as police were closing in.

Brinsley, 28, had a history of violence and mental instability. On the day of the shooting, he went on social media to say he was planning to kill police officers.