A bus has crashed into a tree in south London injuring 32 passengers - seven seriously, say police.

The accident happened around 10.50am on Kennington Road near the Imperial War Museum in the British capital, while the number 59 bus was en route to King's Cross.

Emergency services said several passengers had to be freed from the wreckage. A woman (19) and a man were the last to be rescued and are among those most badly hurt.

Clive Robinson, from London Fire Brigade, said workers had to cut through the bodywork of the bus to free several passengers. Ladders were used to reach those on the top deck.

"The actual floor of the bus was starting to collapse and we had to shore that up," he said. Earlier, police reported that two people were in a critical condition.

Among the injured were two police officers who had been travelling on the bus. They were taken to hospital - one with a suspected broken arm.

Kevin Brown, of the London Ambulance Service, said the injuries ranged from bumps and bruises to serious limb and head injuries.

Aerial footage from the scene showed the front of the bus, operated by Arriva, collapsed around the trunk of a tree. Transport for London said there will be a thorough investigation.

Police say they still do not know what caused the crash and will be viewing CCTV footage from inside the bus.

Chief Superintendent Glyn Jones said "At this stage we don't know what's caused the collision - that is subject to an ongoing investigation".