Westminster Underground station, close to parliament, was closed to the public and the building cordoned off.Parliament is in summer recess and most lawmakers are not using the building. Prime Minister Theresa May is on holiday abroad.However, UK's government emergency committee reported it will hold a meeting at 1300GMT to discuss the incident.In March 2017, Khalid Masood, 52, killed four people on nearby Westminster Bridge before he stabbed to death an unarmed police officer in the grounds of parliament. He was shot dead at the scene. It was the first of five attacks on Britain last year which police blamed on terrorism.Britain is on its second highest threat level of "severe," meaning an attack by militants is considered highly likely.Last week, a Muslim convert admitted plotting to kill more than 100 people by driving a truck into pedestrians on London's Oxford Street, the capital's major shopping thoroughfare.In October last year, 11 people were injured when a car collided with pedestrians near London’s Natural History Museum, raising fears of an attack, but police later said the incident was a road traffic accident."My thoughts are with those injured in the incident in Westminster and my thanks to the emergency services for their immediate and courageous response." - PM @theresa_may
— UK Prime Minister (@10DowningStreet) August 14, 2018