London terror attacks: What we know and don't know

The mayhem started when a van careered into pedestrians on London Bridge, and ended when police swarmed and killed three attackers said to be wearing what were later found to be fake suicide vests. London's Metropolitan Police said they first responded to the bridge at 10:08 p.m. (5:08 p.m. ET).

He then confirmed, it is believed that after the bridge attack, a white van carrying the terrorists continued to nearby Borough Market, where they left the vehicle and initiated a stabbing rampage, involving multiple victims.

The British Transport Police said one of its officers was seriously injured after being stabbed as he responded to the incident, but his condition was not said to be life-threatening. In response, she will chair a meeting of the government's Cobra emergency committee on Sunday.

The Independent reported that Police confirmed that six people have died and up to 20 are in hospital. A number of others were treated for less serious injuries at the scene.

London Mayor Sadiq Khan said it was "deliberate and cowardly attack" on Londoners enjoying a Saturday night out. Trump tweeted: "Whatever the United States can do to help out in London and the U".

One witness told Reuters that she saw what appeared to be three people with knife wounds and possibly their throats cut at London Bridge. I could see it hitting people.

The US embassy in London tweeted: "Please avoid the area and monitor local news/@metpoliceuk for updates".

The cafe stabbings occurred in Borough Market, a popular market with gourmet food and produce stalls and several restaurants inside. "But they said later that turned out to be an unrelated stabbing".

Sky News also reported multiple shots fired and stabbings in the Borough Market area. We need the courts to give us back our rights. Later they said that call was not related to the bridge or cafe incidents.

Armed police have been deployed around London Bridge which is already closed. "There is no justification whatsoever for such barbaric acts", he said.

The attacks come days ahead of a June 8 election and less than two weeks after a suicide bomber killed 22 people at a pop concert by US singer Ariana Grande in Manchester in northern England.

Streets around London Bridge and Borough Market, fashionable districts packed with bars and restaurants, would have been busy with people on a Saturday night out.

Video clips circulating on social media showed police officers rushing into bars and restaurants to instruct customers to get under the tables.

Earlier, British Prime Minister Theresa May said her thoughts were with those caught up in the "dreadful events".