The officer - believed to be Catholic and named locally as James Doherty (43) - was ambushed in Bishop Street in Londonderry city centre about 8.30am, as children were being dropped off at three nearby schools.

The wounded policeman was able to drive himself to a nearby PSNI station to receive first aid.

His injuries were described as serious but not life-threatening.

Deputy First Minister Martin McGuinness, who lives in the city, made a significant call for anyone with information about the shooting to pass it on to police.

There were unconfirmed reports that a shotgun was used in the incident.

A car believed to have been used in the shooting was found on fire in the High Park area of Creggan shortly after 9am.

A PSNI spokeswoman confirmed today: "An off-duty police officer has been injured following a shooting incident in the Bishop Street area at around 8.30am this morning.

"The extent of his injuries is not yet known, but they are not thought to be life-threatening."

The shooting occurred as hundreds of children began arriving at Lumen Christi Grammar School, Nazareth House Primary and Nursery School and nearby Long Tower Primary School.

Early reports suggest that the wounded officer was leaving his child off at one of the local schools, but all three schools today said they were unaware of any pupils or parents caught up in the incident.

Mr McGuinness indicated that he believed dissidents were behind the attack and said that they were "re-attempting to plunge our society back into conflict".

"I am confident that the vast majority of people here will ensure that this does not happen," he said.

He said dissident republicans "have no popular support and have no strategy to achieve a united Ireland".

He added: "The war is over. It is time these people woke up to that reality."

DUP MP Gregory Campbell called upon the community in the largely nationalist Bishop Street and wider Bogside/ Brandywell area to come together and condemn the shooting attack.

Mr Campbell said: "This is a totally reprehensible act. It was wrong to shoot a police officer 10 years ago and it is wrong to shoot a police officer today."

Referring to the vigil held last night in solidarity with a US student raped in the neighbouring Bogside estate at the weekend, Mr Campbell added: " We need to see right across the community the kind of revulsion that, for example, was seen last night when an entire community came out and registered their opposition to the attack on a young woman.

"Hopefully that community will respond in the same way to this violent attack."

Police cordoned off a large area on Bishop Street, from outside Lumen Christi College to the junction with Abercorn Road, a quarter of a mile away.

Foyle SDLP MLA, Pat Ramsey condemned the attack and said everyone had " a moral responsibility" to give information to the PSNI to help stop those who were "intent on murder, mayhem and destruction in this city" .

DUP MLA William Hay said he believes dissident republicans were to blame and described the attack as "an evil, evil act".

He said there were a number of schools in the area, adding: "There were children in the area who witnessed what happened. These people are cowards and there should be no hiding place for people who feel they can still carry out these dastardly deeds."

Policing Board chairman Sir Desmond Rea also condemned "this cowardly shooting".

He said: "This officer joined the police to serve the community.

"We cannot allow those who want to dwell in the past to thwart the progress that has been made. I urge anyone with information to contact the police to ensure those who perpetrated this attack are caught.

"As a society we have moved on with full political support for policing secured.

"I urge anyone with information to contact the police to ensure those who perpetrated this attack are caught."