A man has been arrested between Downing Street and the Houses of Parliament on suspicion of plotting a terror attack.
Police said they stopped and searched the man, in his late twenties, and recovered knives from him, on Whitehall, the main road running through the heart of Westminster.
Reporters on the scene said they saw “knives on the ground” while others said knives fell from the man’s backpack. No one was injured, police said.
Photos from the scene show the man being held against a wall by officers.
Other pictures show forensic officers dusting for prints and taking photographs near the scene.
The Metropolitan Police said: “A man has been arrested in Whitehall this afternoon, at approximately 14:22, following a stop and search as part of an ongoing operation.
“He is being detained under the Terrorism Act and is in custody in a south London police station.
“Detectives from the Counter Terrorism Command are continuing their investigation, and as a result of this arrest there is no immediate known threat.”
As the incident unfolded just before 2.30pm (BST), Reuters reported a witness who said Whitehall was closed to traffic. Danny Shaw, a BBC reporter, said two knives were seen “on the ground”.
The incident took place on the junction of Parliament Street and Parliament Square alongside Whitehall - an area normally bustling with workers and tourists.