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.

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 Islamic extremism.

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

The deadly stabbing of Amess is the second murder of a sitting British lawmaker in five years, after Labour Party member of parliament Jo Cox was killed in her constituency in 2016.

The latest stabbing brings back "the pain, the loss, but also how much love the public gave us," Cox's husband, Brendan Cox, tweeted after Amess's killing.

(With input from agencies)