LONDON: Three assailants stabbed passers-by at random after smashing into pedestrians in a van, killing six people in a "terror attack" in a popular nightlife hub in London before being shot dead by armed police.

Prime Minister Theresa May's Conservative party suspended campaigning for this week's general election following Saturday night's attack, which came less than a fortnight after 22 people were killed in a suicide bombing at a concert in Manchester.

As they rampaged through the bars around London Bridge, the attackers wore what looked like suicide vests which turned out to be "hoaxes", said Mark Rowley, head of counter-terrorism policing.

"We believe that six people have died in addition to the three attackers shot dead by police" in what is being treated as a "terrorist incident", Rowley said.

Forty-eight people were rushed to hospitals in the area, according to the London Ambulance Service.

"They were stabbing everyone. They were running up and going 'This is for Allah'," a man called Gerard told the BBC, adding that he had seen the assailants stabbing a girl and had tried to confront them.

Another witness called Eric told the BBC he had seen three men come out of a white van after hitting pedestrians and thought they were going to help.

But instead they "started kicking them, punching them and took out knives. It was a rampage really," he said, adding that he also heard a shout of: "This is for Allah".

France said two of its citizens were injured in the attack, one seriously, and President Emmanuel Macron, said his nation -- which has suffered its own wave of terror attacks -- was "more than ever at Britain's side."

The injured also included a police officer who was one of the first responders on the scene and was stabbed in the face and leg.

Police said the three men were shot by a police armed response team within eight minutes of receiving the first call at 10:08 pm (2108 GMT).

Conservatives suspend campaign

The attack came only minutes after the end of the Champions League final between Real Madrid and Juventus, in an area teeming with bars where many fans were watching the football on television.

Britain is on high alert only 12 days after a suicide bomber killed 22 people at the concert in Manchester, northwest England, and ahead of the June 8 vote, in which security is a major theme.

"The Conservative party will not be campaigning nationally today. We will review as the day goes on and as more details of the attack emerge," a spokesman for the ruling centre-right party told AFP.

May was due to chair an emergency cabinet meeting on Sunday morning.

"Our thoughts are with those who caught up in these dreadful events," May said in a statement.

It is the latest in a string of attacks to hit Europe, including in Paris, Berlin and Saint Petersburg.

German Chancellor Angela Merkel echoed Macron's message of solidarity, saying her country was "resolutely at Britain's side".

"Today we are united across borders in horror and mourning, but also in determination," she said.

US President Donald Trump offered his help, tweeting "WE ARE WITH YOU. GOD BLESS!" -- and highlighting his thwarted ban on travellers from six mainly Muslim countries.

US pop star Ariana Grande, whose concert in Manchester was the scene of last week's fatal terror attack, tweeted: "Praying for London".