A police boat carrying armed officers has crashed near Westminster Bridge in central London, police sources have said.
Casualties could be seen being treated by paramedics on a rigid black inflatable boat moored to the side of the river.
Officers have taped off a section of the bridge overlook the Houses of Parliament.
A large number of police officers, fire crews and ambulances are on the scene, with traffic across the bridge at a standstill.
A Port of London Authority spokesperson said: “We are aware of an incident involving a police vessel at Westminster Bridge.
“We are supporting the response and providing assistance where needed, working closely with the Metropolitan Police, HM Coastguard and partner agencies to manage the situation.”
A police helicopter and an air ambulance were circling above.
Entrances three and four to Westminster Underground station have been shut, Transport for London has confirmed.
Read MoreMajor London Bridge cordoned off after police boat crash as ‘casualties treated’
