Bomb disposal experts are examining a suspect device found under the car of a police officer in Belfast.
The security alert on the Upper Newtownards Road in the east of the city has seen a number of homes evacuated.
Army technical officers are working to establish if the device is a viable bomb.
SDLP Policing Board member Conall McDevitt condemned the apparent bid to target the officer:
This is a cynical and deplorable act.
Those seeking to target police officers are undermining not only the stated will of the people of Ireland who have long since rejected violence, but also the desire for a new beginning for policing in the North, which is shared by the majority of citizens.
More top news
Ireland's new laws on gay marriage will be enacted by the end of July, with the first ceremonies likely in the autumn.
Stars such as Simon Cowell and Stephen Fry called on their Twitter followers to retweet missing person appeals for 24 hours.
Norwich have been promoted to the Premier League after a 2-0 victory against Middlesbrough at Wembley Stadium.