A week after the London Bridge attack, Londoners are being urged to go out and enjoy the city on Saturday night, with bars and restaurants donating a share of their takings to a Red Cross fund set up for the victims.

The Red Cross is urging people to "take a ride for London, eat a dish for London and say cheers for London."

Among the outlets taking part are restaurants around Borough Market, where attackers stabbed five people to death after mowing down pedestrians on London Bridge, killing three. The market itself remains closed because of the police investigation.

Mayor Sadiq Khan says Londoners are showing "how we pull together in the face of adversity."

Khan says "our resilience, unity and defiance of those evil individuals who seek to harm us and destroy our way of life will never change."

Earlier Saturday British police arrested two more people over the London Bridge attack, and said the carnage could have been worse had the attackers succeeded in their goal of renting a truck, rather than a van, to mow down pedestrians.

Britain London Bridge Attack

A photo issued by the Metropolitan Police shows the van used in the London Bridge attacks last Saturday. Police say one of the attackers had tried to rent a larger truck, but his payment did not go through. (Metropolitan Police London via Associated Press)

The bloodthirsty gang was also shot dead before they could make their way back to the van where their petrol bombs were stored.

London's Metropolitan Police said Saturday they arrested a 27-year-old man and a 28-year-old man overnight in east London on suspicion of preparing acts of terrorism. Police have seven people in custody over suspected links to the three attackers who killed eight people, including Canadian Christine Archibald, on and around London Bridge on June 3.

'The effect could have been worse.' - Dean Haydon,  Metropolitan Police's Counter-Terrorism Command

Police released details of their investigation as they appealed to the public for information, saying Khuram Butt, believed to be the plot's ringleader, originally tried to rent a 7.5-ton truck. The intended truck was smaller but similar to the one used in the Nice attack last year that killed 86 people and injured hundreds in the resort town in the south of France.

After his payment was declined, Butt and his two accomplices rented a smaller van that they used to plow into crowds before they leapt from the vehicle and went on a stabbing rampage in an attack that left eight people dead and nearly 50 injured. It was the third deadly attack in Britain in three months.

After leaving the small white van, the men used 30.5-centimetre-long knives with bright pink blades, according to Dean Haydon, head of the Metropolitan Police's Counter-Terrorism Command.

Police also disclosed that more than a dozen petrol bombs and two blowtorches were discovered in the van, and a copy of the Qur'an opened at a page "describing martyrdom" was found at one of the attackers' houses.

Investigators believe three people were killed on the bridge, including one man who was thrown into the River Thames, before the attackers left the vehicle and stabbed five people to death around London's busy Borough Market, Haydon said. Police believe Butt was driving the van.

"When I come back to Butt trying to get hold of a 7.5-ton lorry — the effect could have been even worse," he said.

Haydon said the men may have been planning even more bloodshed if they made it back to the van.

Britain London Bridge Attack Commissioner

Commissioner of the Metropolitan Police Cressida Dick spoke to Associated Press at New Scotland Yard in London Saturday. She said police had spoken to about 300 witnesses from around 20 different countries of origin, adding that Londoners value the international nature of the city. (Tim Ireland/Associated Press)

Police also found a number of office chairs, gravel and a suitcase in the van.

Detectives believe the gravel may have been placed in the vehicle to make it heavier, or as part of a cover to justify hiring it, while the chairs may have been used to convince family and friends they were moving furniture.

Knives 'pretty unusual'

Butt, a 27-year-old Pakistan-born British citizen, and his two accomplices, Rachid Redouane, 30, who claimed to be Moroccan-Libyan, and Youssef Zaghba, a 22-year-old Italian national of Moroccan descent, were shot dead by armed police eight minutes after the first emergency call.

The three attackers were wearing fake suicide belts consisting of plastic water bottles wrapped in gray duct tape.

Haydon described the pink knives as "pretty unusual" and appealed for anyone with information about where they came from to contact police.

Police raided Redouane's small residence on Tuesday and said he had been renting it since April. This was the safe house where the attack was planned, police said. In the residence, police said they found an English-language copy of the Qur'an opened at a page describing martyrdom, pieces of cloth which appeared to match material wrapped around the petrol bombs and water bottles similar to those used in the fake suicide vests. Luggage straps, plastic retractable craft knives and rolls of duct tape were also found.

The question remains how the men met and knew one another but police said Saturday they did not suspect a wider plot.

"It looks as if it is pretty much a contained plot involving the three of them, which is supported by the forensic evidence we've got back so far," Haydon said.

People gather for a vigil in Potters Fields Park in London

People gather for a vigil in Potters Fields Park in London on June 5 to commemorate the victims of the attack on London Bridge and at Borough Market. (Daniel Leal-Olivas/AFP/Getty Images)

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.

Cressida Dick told The Associated Press in an interview Saturday: "It's desperately sad and poignant, but among those who died is someone who's British, there are French, Australian, Canadian, Spanish."

"In terms of our witnesses that we've spoken to so far, out of the 300 odd people, there are about 20 different countries of origin. And the London British population comes from all kinds of backgrounds and every kind of faith and ethnicity."

She said longtime Londoners value the international nature of the British capital.

"We believe of course that that's what makes our city so great," she said.

None of the attackers had convictions

Butt had been on bail after being arrested for fraud in a case in October, police said. He had also been repeatedly reported to police for violent behavior and trying to recruit young children to the Islamic State group, and appeared in a TV documentary titled The Jihadis Next Door, where he was seen next to a group of men unfurling a black-and-white flag scrawled with Arabic script and associated with ISIS.

But Haydon said "there was no evidence uncovered of any attack-planning in relation to him."

Butt had been warned by police on two occasions — once for fraud in 2008 and once in 2010 for assault. Still, he did not have any criminal convictions.

Zaghba and Redouane had no criminal convictions or such warnings in Britain.

"From what I'm seeing, there is nothing that suggests at the moment that we got that wrong," Haydon said, referring to Butt.

Meanwhile, two of British Prime Minister Theresa May's top aides resigned Saturday following a disastrous election campaign that was overshadowed by the attacks.