Three children have been injured – one of them seriously – in a knife attack at a daycare centre in the Swiss city of Zurich.

A spokesperson for the city’s police force said a 23-year-old Chinese man attacked a group of children who were being led to the centre by a staff member.

A daycare worker and a bystander managed to overpower the attacker and restrain him until police arrived.

A five-year-old boy suffered serious injuries and was being treated in hospital. Two other five-year-old boys were treated at the scene for less severe injuries.

Officers have yet to reveal a motive for the attack, which took place shortly after 12:00 local time (11:00 BST) in the near the Bernina shopping centre in Oerlikon, an area in the north of Zurich.

Police said an investigation was continuing and local media reported heavily armed officers were guarding the scene on Tuesday afternoon, while a drone flew overhead.

NZZ, a Swiss media outlet, said police searched a residential building near the daycare. It is unclear whether the operation was connected to the attack. (BBC)