Westminster assailant was British-born and known to MI5: May

UK Prime Minister Theresa May says the Westminster assailant was British-born and known to the country’s domestic intelligence agency, MI5, and had been investigated before.

"What I can confirm is that the man was British-born and that some years ago he was once investigated by MI5 in relation to concerns about violent extremism," she told MPs on Thursday, a day after an attack outside the UK Parliament in London which left at least four people dead and 40 others injured.

"He was a peripheral figure," she added. "The case is historic, he was not part of the current intelligence picture."

She added that "when operational considerations allow, he will be publicly identified.”

In a defiant speech to the Parliament, May said, "We are not afraid and our resolve will never waver in the face of terrorism."

Lawmakers earlier held a minute's silence in honor of the victims.

The assailant plowed a car on Wednesday into pedestrians and stabbed a police officer, an incident that has been declared a terrorist incident.

Police have arrested eight people during the investigation into the incident.

MI5 Director General Andrew Parker earlier said his agency had fully mobilized its operational response in support of the police.

"We stand shoulder-to-shoulder with our police colleagues, grieving at their loss while also applauding the professional excellence of their response," he said in a statement.

SS