British Prime Minister Boris Johnson on Saturday visited the church where lawmaker David Amess was stabbed to death a day earlier in what police say they are treating as a terrorist attack.

Amess, 69, from Johnson's Conservative Party, was knifed repeatedly in the attack at about midday on Friday in Leigh-on-Sea, east of London, during a meeting with constituents.

Johnson, interior minister Priti Patel, and leader of the opposition Labour Party Keir Starmer were among those to lay flowers in tribute to Amess at the scene of the murder.

Johnson and Starmer stood side by side in a moment of silence before leaving. On Friday, Johnson said Britain had lost a fine public servant and a much-loved friend and colleague.

In a statement early on Saturday, police said the early investigation had revealed a potential motivation linked to extremism.

Police arrested a 25-year-old British man at the scene on suspicion of murder, adding it is believed he acted alone.

As tributes poured in for Amess, politicians described the attack as an assault on democracy, and Patel said security for lawmakers, known as MPs, was being reviewed and strengthened.

“All measures are being put in place for the security of MPs so that they can carry on with their duties as elected democratic members,” Patel said in a broadcast clip following the visit.

“We live in an open society, a democracy. We cannot be cowed by any individual.”

In Westminster, where lawmakers do much of their work in parliament, armed police are on patrol. But in their electoral districts, known as constituencies, more often than not there is no security.

Amess was stabbed while holding a surgery — one-to-one meetings with voters, open to whoever turns up.

Conservative lawmaker Tobias Ellwood said that while engagement with the public was a vital part of the job, there was now huge anxiety among MPs and called for a pause in such meetings.

Patel said Amess was killed doing a job he loved, and lawmakers should remain accessible to the public.

“We will continue to absolutely stand by the principles that we are elected by: to serve our constituents in the open way in which we have been doing so, but also recognising that there are safety and protection measures that we have to undertake too,” Patel said.

Amess in the second lawmaker in little over five years to be murdered while out meeting constituents, after Jo Cox was shot and stabbed in June 2016, a few days before Britain voted to leave the European Union.