Forensics officers work near the car that crashed into security barriers outside the Houses of Parliament in London, Tuesday, Aug. 14, 2018. (Photo: AP)

LONDON, Aug. 14 (Xinhua) -- The Westminster attack is "shocking" and terror threat level remains severe in the United Kingdom, a spokesman for British Prime Minister Theresa May said here Tuesday.    

The spokesman described the car crash outside the British Parliament on Tuesday as "shocking". At least three people were reportedly injured as the car hit cyclists and pedestrians.

A man in his late 20s, who drove a silver car "at speed" during the morning rush hour, has been arrested on suspicion of terrorism offences and the police treated the car crash as a "terrorist incident."

The suspect is reported to be from the Midlands and it is believed that he might have travelled to London from Birmingham.

Streets around Parliament Square, Millbank and Victoria Tower Gardens were also cordoned off as dozens of armed police swooped on the scene.

The Met Police Counter-Terrorism Unit is leading an investigation into the incident which took place at 7:37 a.m. (BST) on Tuesday.

Meanwhile, the spokesman also said that 13 Islamist plot and four far-right plots have been successfully foiled since March 2017, when Khalid Masood ploughed a car into crowds on Westminster Bridge, killing four people. Masood abandoned his car then stabbed and killed unarmed PC Keith Palmer before he was shot by armed police in a courtyard outside Parliament.

Cover image: Police forensics officers work around a silver Ford Fiesta car that was driven into a barrier at the Houses of Parliament in central London on August 14, 2018. (Photo: AFP)