A man with a knife was arrested Friday near the House of Parliament, British police said.
The man, said to be in his 30s, was detained just after 11 a.m. local time, Metropolitan police said. Photos from the scene showed three or four officers handcuffing the man. He was taken to the London police station and remains in custody.
There were no injuries reported, according to police.
The incident was declared not terror-related, though authorities are remaining "open-minded as to whether terrorism" was a factor, police said. They said it's too early to "understand" the man's motive is at this time.
The Westminster Palace is the meeting place of the two houses of Parliament in England.
The incident comes just months after a man slammed his car into a group pedestrians on Westminister Bridge, then jumped out of the vehicle and stabbed a police officer to death.
England has been reeling from two recent terror attacks that killed dozens of people. The country's terror threat level is at severe after it had been raised to critical.