An undated handout photo issued by the Metropolitan Police, London, and made available on Sunday June 11, 2017 of fake suicide belts worn by one of the London Bridge attackers in the attacks of Saturday June 3 which killed several people and wounded dozens more.
Counter-terrorism officers arrested two men in a street and another man in a separate raid on a house in Ilford, east London, late on Wednesday night, Scotland Yard said.
Detectives from London police's counterterrorism command raided properties in east London on Thursday, detaining three people on suspicion of the commission, preparation or instigation of terrorism offenses.
Police Commander Dean Haydon said the attackers may have worn the belts because they planned to take hostages, "or it might be that they saw it as protection from being shot themselves".
Searches of the residential address and a business address in Ilford are ongoing.
There is no sound on the CCTV but we know that 48 rounds were fired by eight police officers.
"I am so proud of my colleagues from BTP and everyone from the other emergency services who were on shift that night and did everything they could in the face of danger".
Investigators believe three victims 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.
Reaction to the attack has dominated the final days of campaigning before Thursday's general election in Britain.
All three men were taken into custody at a south London police station.
The latest arrests are not connected to the London Bridge attack, the Met confirmed.
Butt, 27, was a British citizen born in Pakistan who was known to security services, while Italian authorities said they warned the United Kingdom that 22-year-old Zaghba was a "possible suspect".
Police named Barking as the home of two of the attackers - Khuram Shazad Butt and Rachid Redouane - while their accomplice Youssef Zaghba was listed as being from east London.
Redouane, a 30-year-old who described himself as Moroccan-Libyan, did not come up on MI5's radar. "But one of those animals could detonate and kill us all".
Kaine Pieri said he was about to cross the bridge to catch a bus when police descended on the white van used in the attack and people ran by screaming, desperate to get away.
A 33-year-old was arrested on suspicion of possession with intent to supply controlled drugs.