(Yui Mok/PA via AP).
Seven people were killed and 49 injured when the trio rammed a van into pedestrians on London Bridge before stabbing revellers in bars in the nearby Borough Market.
The three attackers, wearing fake suicide bomb vests, were shot dead by eight officers outside a pub after police fired 50 bullets.
The Islamic State in Iraq and Syria (ISIS) extremist group, which is losing territory in Syria and Iraq to an offensive backed by a US-led coalition, said its militants were responsible for the attack, though it is unclear what links the attackers had to the group.
Scotland Yard arrested 12 people under the Terrorism Act in Barking on Sunday, with one subsequently released without charge.
Police have not released the names of the attackers and British newspapers refrained from identifying the men.
He said he then saw a woman and man being stabbed while the attackers shouted: "This is for Allah", and recalled how he tried to distract the men.
IS has claimed responsibility for three attacks in Britain since March, and Dick described the recent wave of violence as "unprecedented in my working life".
She added: "It's not just about numbers, it's about powers, it's about making sure the police have the powers they need".
Prime Minister Theresa May warned that the country faced a new threat from copycat attacks.
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Ms Dick, asked whether she would demand additional officers, told ITV's Good Morning Britain: "Over the last several years, police services have in many respects become, it's a ghastly phrase, but become very much more efficient, they have managed to do things in a more productive manner".
She said: "They were waiting for the children of the neighbourhood".
'But the fact is we need to make sure the police have the resources and support they need, and as the mayor my job is to make our city safe and I'll do my best as the mayor to be an advocate and champion for our police to get the tools they need'. Corbyn called for May to resign because of her role in cutting police staffing during her tenure as home secretary.
"We were all stuck!" said Marcia Rainford, a 58-year-old who said she was sealed into her building complex with her mother and two children.
"We must stop being politically correct and get down to the business of security for our people". In a statement, her family said: "We grieve the loss of our attractive, loving daughter and sister". "I always stock up!"
Police said they had seized a huge amount of forensic material in two early morning raids in east London Monday, as part of their efforts to determine if the three men who carried out Saturday's attack were part of a wider network.
Sadiq Khan praised officers for doing a "fantastic job" with the resources they have but said it was "a fact that, over the last seven years, we as a city have lost £600 million from our budget - we have had to close police stations, sell police buildings and we've lost thousands of police staff".
She said providing more firearms for London police wouldn't be a sensible solution to the increased tempo of attacks, saying the strategy of having special mobile units of heavily armed officers is effective.
After the attack police evacuated numerous survivors from Borough Market to Liverpool Street where they took witness statements and kept witnesses inside until Sunday morning.