Three assailants kill 7 in London terror attack

London : Three assailants smashed a van into pedestrians on London Bridge before attacking revellers in a popular nightlife hub with knives, leaving seven dead in the third deadly terror attack in Britain since March.

Britain's main political parties temporarily suspended campaigning for Thursday's general election and Prime Minister Theresa May held an emergency meeting following the rampage on Saturday evening.

"It has now been confirmed sadly that seven members of the public have died," in addition to the three suspects, London police chief Cressida Dick said.

An Australian and four French nationals were among the 48 people rushed to hospital after the attack.

May's Conservatives and the main opposition Labour party suspended national campaign events for the day, joined by other parties, although local campaigning will continue.

Security was already a major feature of the campaign, after 22 people were killed in the Manchester concert bombing on May 22, claimed by the Islamic State group.

As they attacked revellers around London Bridge, the attackers wore what looked like suicide vests which turned out to be "hoaxes", police said earlier.

"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 three assailants stabbing a girl as she cried for help.

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.

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

Dick declined to give any further details about the attackers, but added: "At the moment we believe there were three attackers and we believe they are dead."