All three killers were shot dead.
Eight people died and a further 48 people were injured in what was Britain's third Islamist attack in as many months.
Earlier police, who were hunting for 45-year-old Frenchman Xavier Thomas, missing since the attack, said that they had found a body in the River Thames. His girlfriend was struck by the van and seriously injured.More news: Trump takes sides in Arab rift, suggests support for isolation of Qatar
Abedi killed 22 people and wounded more than 100 when he detonated a bomb at the crowded Manchester Arena, where United States pop star Ariana Grande had been performing.
The families of the London attackers have condemned their actions on Wednesday, with relatives of Khuram Butt, Youssef Zaghba and the ex-partner of Rachid Redouane saying they were shocked at what had happened.
Every one of the 12 people arrested in east London in the wake of the murderous rampage was released without charge. In a statement Tuesday, authorities said they arrested a 27-year-old man Tuesday morning.
Citing intelligence sources, Italian dailies Corriere della Sera and La Repubblica said Zaghba was met at the Bologna airport by Italian intelligence agents each time he arrived in Italy to visit his mother after his initial run-in with Bologna airport authorities on March 15, 2016.More news: Apple to showcase new features for its gadgets
One of Butt's neighbours, Ikenna Chigbo, told Reuters he had chatted with Butt - known locally as "Abz" - just hours before the attack on Saturday and said he appeared "almost euphoric".
Authorities said they were still trying to identify the third attacker. Butt was a British citizen born in Pakistan and was already known to police and Britain's domestic spy agency MI5, London's police force said.
Police said three men - Khuram Shazad Butt, 27; Rachid Redouane, 30; and Youssef Zaghba, 22 - rammed a van into pedestrians on London Bridge before launching a stabbing spree in bars and restaurants at nearby Borough Market on Saturday.
Three men suspected to be involved in terror activities were arrested in London on Wednesday.More news: Schindler prepares for party after seeing Huddersfield into Premier League