A British lawmaker was stabbed to death in a church on Friday by an assailant who lunged at him during a meeting with voters from his constituency, a killing police are investigating as a possible terrorist attack.

David Amess, 69, from Prime Minister Boris Johnson's Conservative Party, was knifed repeatedly in the attack at about midday in the Belfairs Methodist Church in Leigh-on-Sea, east of London.

A 25-year-old man was arrested at the scene on suspicion of murder, and...