A booby trap bomb has partially exploded on an A-road near Belfast, setting fire to a police car.
Army bomb disposal officers were called to the scene after emergency services received a report of a car on fire on the A2 between Northern Ireland's capital and Bangor.
The driver of the vehicle is a serving police officer. She escaped unharmed.
The Police Service of Northern Ireland said the A2 remained closed while Army technical officers examined the vehicle.
Arlene Foster, leader of the Democratic Unionist Party, interrupted a Brexit press conference to address the situation.
"We've just received news from Northern Ireland which is very disturbing," she said. "A booby trap bomb has exploded under a female police officer's car.
"Thankfully she wasn't in it at the time the car went on fire. We do condemn utterly those who would seek to bring violence back to Northern Ireland.
"They failed in the past and of course they will fail again in the future and we urge everyone to work with the police service of Northern Ireland to bring these people to justice."
The incident comes days after MI5 downgraded the threat of a UK mainland terrorist attack by dissident republican groups.
The security agency lowered the assessment from "substantial" to "moderate", which means officials consider an attack "possible but not likely".
In Northern Ireland, however, the threat remains "severe", meaning an attack is "highly likely".
