The attackers had previously tried to hire a seven-and-a-half tonne lorry before using a rented van to ram pedestrians, police said.
Investigators believe three victims were killed on the bridge - including one man who was thrown into the Thames - before the attackers left the vehicle and stabbed five people to death around Borough Market in London. The attacker and two of his accomplices then rented a smaller, white vehicle, which they then drove into crowds of people at London's Borough Market, ultimately leaving eight people dead and almost 50 injured.
Police released an image late Saturday night of one of "the distinctive pink knives used during the London Bridge terrorist attack". "Where might the attackers have bought them from?" the Met's counter-terrorism command chief Dean Haydon said, calling on the public to contact police if they had any information on the weapons.
These included two blow torches and wine bottles with rags wrapped around them containing flammable liquid.
The three men drove the van into central London last Saturday night, running down pedestrians on the pavement of the bridge, three of who died.
"What happened in the last 12 weeks with the attacks in London and Manchester and with the five plots which we have thwarted, which had murderous intent and we stopped them, has only given my officers, my staff, the Metropolitan Police, more resolve, more determination", she said.
Gardaí issued an appeal this morning on behalf of London police for witnesses to the attack to come forward.
A woman attaches a sign near London Bridge after the attack.
Police also released photos of the van the attackers used to mow down people on the bridge.
Although Islamic State in Iraq and Syria (ISIS) militants have claimed responsibility for the attack, Haydon said there was no evidence the attackers - Pakistani-born Briton Khuram Butt, Italian Youssef Zaghba and Rachid Redouane who had links to Libya, Morocco and Ireland - were directed by anyone else, either in Britain or overseas.
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The commissioner of London's Metropolitan Police says the nationalities of the eight victims in the terrorist attack on London Bridge tell a proud story of London's unique makeup.
Mr Haydon said: "When I come back to Butt trying to get hold of a 7.5-tonne lorry - the effect could have been even worse".
Overall, police searched 12 properties in Barking and nearby Ilford, arresting 18 people.
The police and intelligence agencies have tried to prevent complex, high-tech plots - such as those created to bring down commercial flights - but now they are dealing with a rash of less complicated attacks on soft targets, she said.
In a raid of an east London apartment rented by Redouane, police found an English-language copy of the Quran opened at a page describing martyrdom and materials that may have been used to make the Molotov cocktails. Butt's knife also had a leather strap attached to the handle to keep the knife secured around his wrist.
"We've been working round the clock to understand what these men did in the lead up to the attack, but we need to know more about these unusual knives", Haydon said.
Butt had been on bail after being arrested for fraud in a case in October, police said.
"There was no evidence uncovered of any attack-planning in relation to him", Haydon said.
Zaghba and Redouane had no criminal convictions or such warnings in Britain.
She said: "We, in this city, have experienced terrorism for as long as I've been alive and we have always been able to step up and deal with a new threat and that's what we're going to do here".
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