NEW YORK (AFP/REUTERS) - A plainclothes police officer was seriously wounded by a gunshot to the head in New York, the police said on Saturday, and the authorities said a suspect had been arrested and was in custody.

The 25-year-old police officer Brian Moore was shot in the head while inside his car in the city, police commissioner Bill Bratton said during a press conference, describing it as a serious injury.

The officer had surgery after being admitted to the hospital. Officer Moore was in critical but stable condition following surgery at Jamaica Hospital Medical Center about four hours after the shooting, a hospital representative told reporters on Saturday night.

Local media reports said officer Moore had been placed in a medically induced coma.

According to Mr Bratton, officer Moore and another officer were in an unmarked car when they saw a man adjust something on his belt, whom they approached.

The man fired immediately, Mr Bratton said, while the two officers were still in the car.

The alleged shooter was arrested just over an hour later, the police said. The police arrested Demetrius Blackwell, 35, who shot at officer Moore and another officer at about 6.15pm while they were in their car in a middle-class neighborhood in the borough of Queens, Mr Bratton told reporters.

Mr Bratton said the officers were trying to question Blackwell, who had an extensive criminal background, after they observed him appearing to adjust an object in his waistband.

Blackwell "removed a firearm from his waistband and ... fired several times into the vehicle," Mr Bratton said, adding that"both officers were still seated in the vehicle and did not have an opportunity to get out or return fire".

Local media reports said that Blackwell had been paroled recently after serving seven years in prison for attempted murder.

New York Mayor Bill de Blasio said officer Moore was "very, very seriously injured".

The local media reported the officer had been shot in the face. "It's a reminder of the dangers all of our officers face every single day," Mr de Blasio told a news conference at the hospital.

Mr de Blasio said officer Moore came from a police family and has served with distinction.

This is the fifth shooting of an officer in New York in five months.

In December, two officers were shot dead in their car in New York by a man who then committed suicide.

That shooting was seemingly motivated by anger over the death of an unarmed black man killed by New York police.

The shootings come at a time of increased national focus both on the use of force by law enforcement officers and the dangers of police work. On Friday, six officers were charged in the death of a Baltimore man who was injured while in police custody.

Mr de Blasio's relations with New York City police fell sharply after two city officers were shot and killed in December as they sat in their patrol car, in what officials said was a targeted attack.

Hundreds of officers turned their backs when Mr de Blasio delivered a eulogy at one of the officer's funerals, angry at what they saw as his failure to support them during a wave of anti-police protests in the city late last year.