Police are dealing with a "major incident" on London Bridge, Transport for London said on Saturday, as well as another incident in nearby Borough Market with "armed police at the scenes".

"As well as #LondonBridge officers have also responded to an incident in #BoroughMarket. We have armed police at the scenes," police tweeted at 22.20 GMT.

Less than an hour earlier, the capital's transport agency said on Twitter that police were dealing with a "major incident" at London Bridge and that all routes were being diverted

Witnesses on London Bridge reported seeing a van mounting the pavement and hitting pedestrians.

The London Ambulance Service said "multiple resources" were being sent to the scene.

Will Heaven, managing editor of The Spectator, said on Twitter that he saw "two casualties -- one on pavement, one edge of road" and reported seeing armed police on the bridge.

BBC reporter Holly Jones, who was there at the time of the incident, said she saw a van driven by a man travelling "at about 50 miles an hour".

She said about five people were being treated for injuries after the vehicle mounted the pavement and hit them.

"There's several police boats with torchlights searching the Thames at the moment," she told BBC radio.

She added that she saw a man, who had his shirt off and was in handcuffs, being arrested by police.

The latest incident is reminiscent of the Westminster Bridge terror attack in which five people were killed and more than 50 wounded.

The attacker, 52-year-old British Muslim convert Khalid Mahmood rammed his car into pedestrians before crashing into the barriers surrounding parliament and then stabbing a police officer to death.

He was then shot dead by police at the scene. Investigators later described the lone-wolf attack as "Islamist related terrorism".

It also comes less than two weeks after 22 people, including seven children, were killed in a suicide bombing at the end of a pop concert at the Manchester Arena.

Manchester-born Salman Abedi, a 22-year-old of Libyan origin, was named as the bomber.