Police say seven people were killed and 48 others injured when a white van mowed down pedestrians on London Bridge in the city's centre, and three attackers wearing fake suicide bombs were shot dead after stabbing several victims at nearby Borough Market.

Prime Minister Theresa May held an emergency meeting of COBRA, the government committee that coordinates intelligence matters and afterwards said:

"The whole of the country needs to come together to counter this extremism. We need to review our counter-terrorism strategy, to see police have everything they need."

She added: "It is time to say enough is enough."

Britain's Prime Minister Theresa May speaks outside 10 Downing Street after an attack on London Bridge and Borough Market left 7 people dead and dozens injured in London, Britain, June 4, 2017. [Photo/Agencies]

May said the three recent attacks in the UK - in Westminster, Manchester and London Bridge – in the recent months were not connected, but said attackers could be inspiring and copying each other.

She said: "We are experiencing a new trend in the threat we face as terrorism breeds terrorism."

May confirmed that Thursday's general election will go ahead, and her ruling Conservative Party and the opposition Labour Party had agreed to would temporarily suspend national campaigning for a day, although UKIP said it would carry on as usual, because halting the campaign "was precisely what the terrorists want us to do," accord to leader Paul Nuttall.

Last night's attack followed a suicide bomb at an Ariana Grande pop concert in Manchester when 22 people, mainly young pop fans, were killed and 116 injured.

In March five people were killed when a man, later identified by police as a suspected Islamic extremist, drove a car at pedestrians on nearby Westminster Bridge before being shot dead by police.

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