KARACHI, Pakistan (AA) – At least one policeman was killed and four others injured in a suicide blast in Pakistan’s capital Islamabad on Friday, police said.

The Islamabad police tweeted police were conducting snap-checking when they signaled a suspicious vehicle to stop.

“A suicide bomber aboard the vehicle detonated himself soon after the car stopped,” it said.

Sohail Zafar Chatta, DIG Islamabad, told reporters later that a man and a woman were aboard the car.

The police said the explosion was caused by some explosive material placed inside the vehicle.

Islamabad has been under security alert for the last several days, following the taking over of a counter-terrorism facility in the northwestern Bannu district this week.

Security forces took control of the Parliament House earlier this week amid a security threat.

Footage aired on Geo News showed the taxi lying overturned in the middle of a road with plumes of fire wafting upwards

There was no immediate claim of responsibility for the incident.