London was stunned Saturday night by attacks that killed seven people in the center of the capital. A van ran down pedestrians on London Bridge, then continued to nearby Borough Market, where three attackers emerged and began stabbing people, the police said. Armed officers responded and killed the assailants, who were wearing fake explosive vests, the police said.

Witnesses described scenes of confusion and panic. Restaurants and hotels were evacuated, and helicopters hovered over the scene. The London Ambulance Service said it had brought at least 30 injured people to hospitals.

There was no immediate claim of responsibility for what the police called a terrorist incident. It came less than two weeks after the bombing in Manchester that killed 22 people at a pop concert, including many children. And it was strikingly similar to the March attack at Westminster Bridge in London, where a driver killed four pedestrians before fatally stabbing a police officer. He was shot and killed by the police near Parliament.