A Scotland Yard spokesman said: "Detectives investigating the London Bridge terror attack have made three more arrests and carried out two more search warrants in east London on Wednesday". A 29-year-old man apprehended at the llford home was also arrested on suspicion of the preparation of terrorist acts.
The three were taken into custody at a south London police station under the Police and Criminal Evidence Act.
Three men - Khuram Butt, Rachid Redouane and Youssef Zaghba - drove into pedestrians on London Bridge on Saturday evening (local time) before stabbing passers-by with knives, killing eight.
Eight people died and 48 were injured in the attacks, including four unarmed policemen who had attempted to tackle the terrorists to the floor.
The operation took place overnight and searches are ongoing at the properties, the force said.
Twelve people were initially arrested after the attack but they were later released without charges, Metropolitan Police said Monday.
The arrests come after a officers detained a 30-year-old man following a raid at an address in the same borough in the early hours of Wednesday.
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".
Abedi killed 22 people and wounded more than 100 when he detonated a bomb at the crowded Manchester Arena, where USA pop star Ariana Grande had been performing.
As part of the bombing investigation 21 people have been arrested, of whom 12 are now free.