Two of Britain's main parties, including the ruling Conservative party, on Sunday decided to suspend its campaign for the general election after the terrorist attack in London, which killed six persons and injured 48 others.

The ruling Conservative party announced that it was suspending its campaign following the attack just days before the polls on June 8 involving a van and three terror suspects, who were shot dead by Metropolitan Police armed officers.

"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 Tory party spokesperson said.

The Opposition Labour party has also indicated that all planned campaign events for today would be called off.

The Scottish National Party (SNP) has also called off its campaign for today.

However, the suspension will not include local campaigning, and local candidates will have the freedom to use their judgement.

London mayor Sadiq Khan said he is "passionate believer in democracy" and would not want to see the election date being affected by the latest incident.

"There can be no justification for the acts of these terrorists and I'm quite clear we'll never let them win nor we will allow them to cower our city or Londoners," he said.

A white van hit pedestrians on London Bridge last night before three men got out and stabbed people in nearby Borough Market, a very busy area of central London.

Scotland Yard said the three men were wearing what looked like suicide bomb vests, which later turned out to be fake.

All three suspects were shot dead by armed officers on the scene within eight minutes.

"We are treating this as a terrorist incident and a full investigation is already under way," said Metropolitan Police Assistant Commissioner Mark Rowley.

The latest attack is the third terrorist strike in the UK this year, with campaigning also suspended for three days last month after suicide bomber Salman Abedi killed 22 victims at a concert in Manchester on May 22.

Earlier this year, on March 22, terror suspect Khalid Masood mowed down four pedestrians to death before stabbing to death a police officer on duty at the UK Parliament.