Britain has been sent reeling after its capital city was attacked by armed men who launched an assault that left seven people dead and the country stunned, less than a week before the General Election.

Three attackers were shot dead after the van and knife attack at London Bridge and Borough Market, locations less than half-a-mile apart, which injured at least 48 people.

They brought carnage to the streets of the capital, stabbing a police officer and revellers with 12-inch knives, reportedly shouting "this is for Allah".

The trio were pictured wearing what appeared to be explosive vests, which Scotland Yard later confirmed were hoaxes.

General election campaigning has been suspended in the wake of the attack.

On London Bridge, eyewitnesses reported seeing several people lying injured on the pavement or the middle of the road, after a white van began mowing people down some time after 10pm.

Police said the suspects then made their way to Borough Market and started attacking people with people with knives. There were reports of Londoners out for a Saturday night, fending off the attackers with chairs and glasses.

Mark Rowley, Assistant Commissioner at Scotland Yard, said one of the injured was an on-duty British Transport Police officer, who was stabbed in the face, head and leg as he tried to fend off the attacker. His injuries were described as serious but not life-threatening.

Mr Rowley said the suspects were wearing what appeared to be suicide vests, but these were later revealed to be fakes.

A taxi driver, speaking the BBC, described the moment when it became clear that terrorists were attacking the city.

“A van came from London Bridge itself, went between the traffic light system and rammed it towards the steps," he said.

“It knocked loads of people down. Then three men got out with long blades, 12 inches long and went randomly along Borough High Street, stabbing people at random.”

Amid the carnage and some confusion about how many attacks were taking place, the Metropolitan Police said in a tweet: “Please remain calm, but be alert & vigilant. We are using all necessary skills & resources at #LondonBridge #BoroughMarket #Vauxhall.”

The attack came just days before the country goes to the polls in the General Election on 8 June, and less than two weeks after a 22-year-old man detonated a homemade bomb at the Manchester Arena shortly after the conclusion of an Ariana Grande concert, killing 23 people. The 23-year-old American singer was among those who sent her sympathies to London on last night.

Police respond to 'major incident' at London Bridge

Photographs taken outside The Wheatsheaf pub in Borough Market appeared to show two of the three suspects lying prone on the road, being stood over by police. One was wearing some sort of canisters around his waist.

With confirmation that more than one person was involved in the attack, it is of deep concern to the police and security services, as it would indicate a level of planning and organisation many times more serious than that involved in the kind of lone wolf attack outside Westminster in March, when 52-year-old Briton Khalid Masood, drove a car into pedestrians on the pavement and then attacked people with knives, injuring more than 50, four fatally.

Similar attacks in Berlin, Nice, Brussels and Paris have been carried out by militants over the past couple of years.

It was initially reported that police believed a stabbing in Vauxhall was linked to the events on London Bridge, but Scotland Yard said later it was unrelated.

Owen Evans, 39, was in the Wheatsheaf pub on Stoney Street near Borough Market on Saturday night, with friends, when shooting broke out nearby.

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“I was in the back of the pub. A wave of about 30 people ran in and tried to get into the cellar or cupboard. Then there were shots outside. They didn’t seem real – like a kid letting off firecrackers. We saw police lights and everyone got down under a table. People turned tables over,” he told the Guardian.

“We waited about 10 minutes or so, with several shots every couple of minutes. Someone at the front of the pub had been shot – it’s speculation but we thought it was by accident, there were bullet holes in the windows.”

A chef from an Italian restaurant on the edge of borough market told The Independent he heard shouting and ran into the basement with the customers.

“There were people all outside the restaurant,” said the chef, who asked not to be named. “One had been stabbed in the back, others in their legs. They were bleeding. We were on our way out and then we heard gunshots from the other way.”

He added: “The people near the person called for a medic, shouting: ‘He’s f***ing bleeding to death, we need a doctor.’ The bar staff were amazing, I think they locked the door so no one got in.”

A couple of New Zealand tourists from Auckland said they were coming out of London Bridge station when heard shots.

(Gabriele Sciotto ) (Gabriele Sciotto)

“It sounded like a dozen but we didn't know if it was a gun or Taser,” said the woman. “We came down the escalators from The Shard and police were shouting ‘get back, for your own safety get back’.”

The Metropolitan Police confirmed at least one armed officer had opened fire during the attack on Borough Market. In information posted on Twitter they said: “Armed officers responded and shots have been fired.”

The force later confirmed three suspects had been shot dead eight minutes after they received the first emergency call.

The Prime Minister said that “following updates from police and security officials, I can confirm that the terrible incident in London is being treated as a potential act of terrorism”.

She said it was a fast-moving investigation and her thoughts were with “those who are caught up in these dreadful events”.

London mayor Sadiq Khan condemned the “barbaric and horrific” attack as “deliberate and cowardly”.

US President Donald Trump used Twitter to offer help to Britain and also to push his demand for tougher screening and a end to immigration.

“Whatever the United States can do to help out in London and the U.K., we will be there - WE ARE WITH YOU. GOD BLESS,” Mr Trump said in one of two tweets.

“We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban [from several Muslim-majority countries] as an extra level of safety.”