British police said on Tuesday they were dealing with a security incident at London's St Thomas' Hospital, with the nearby Westminster Bridge leading to parliament closed to traffic.
Police said they would provide more information when known.
Witnesses reported on social media that there were armed police present and that the hospital was not allowing people to enter or leave.
There was no immediate comment from the hospital.


Palestinian teen shot dead in Israeli West Bank raid, Wafa reports
Libya says 17 migrants perish at sea, nine missing feared dead
Israel begins intercepting Gaza aid ships far from shores, army radio says
Trump urges Iran to sign a deal and discusses prolonged blockade
Seven people die in hospital wall collapse in southern India