Britain's Prime Minister Theresa May attends the commemoration marking the 100th anniversary of the Battle of Amiens, held at the Amiens Catheral, in Amiens, France, August 8, 2018. Sebastien Courdji/Pool via REUTERS

LONDON (Reuters) - A suspected attack outside the Houses of Parliament on Tuesday is shocking, British Prime Minister Theresa May said, warning that the terrorism threat to the United Kingdom remained severe.

Police said a man deliberately drove a car into pedestrians and cyclists, injuring three people, before ramming it into barriers outside Britain’s parliament. [nL5N1V51YB]

“The threat to the United Kingdom from terrorism remains severe. I would urge the public to remain vigilant,” May, who is out of the country on holiday, said in a statement.

May’s spokesman said she had had regular briefings with security officials throughout the day.