A 47 year old man arrested over the Finsbury Park attack on a group of worshippers near a mosque, has been further arrested on suspicion of the commission, preparation or instigation of terrorism including murder and attempted murder, Scotland Yard said.
One man died and ten people were injured after the driver, described as a large white man, targeted people near the Finsbury Park Mosque in north London early on Monday.
The suspect was detained at the scene and arrested by police.
Images of the van showed it was rented from Pontyclun Van Hire in Pontyclun, near Cardiff. South Wales Police is working with officers from London on the investigation.
Searches are being carried out at a residential address in the Cardiff area in connection with the attack, Scotland Yard said.
Witnesses described hearing the man, who was detained by members of the public at the scene, shout: "I'm going to kill Muslims".
Metropolitan Police Deputy Assistant Commissioner Neil Basu said: "This is being treated as a terrorist attack."
London Mayor Sadiq Khan called the incident an "horrific attack on innocent people."
Finsbury Park is in the Islington North constituency of Labour Party leader Jeremy Corbyn. In a statement he said he would be attending prayers at the mosque later today.