Police officers run at the scene of an apparent terror attack on London Bridge in central London on Saturday night. | DANIEL SORABJI/AFP/Getty Images London attackers killed in ‘unprecedented’ hail of bullets ‘There were three men wearing what appeared to be suicide belts. They had to be stopped immediately.’

The eight police officers who shot and killed the three attackers in central London on Saturday night used 50 bullets, "an unprecedented number of rounds," since they thought they were confronting suicide bombers, a representative of the London Metropolitan Police said on Sunday afternoon.

"This was a matter of life and death: There were three men wearing what appeared to be suicide belts. They had to be stopped immediately," the Met's Assistant Commissioner Mark Rowley said at a press conference. "I’m not surprised that the firearms officers fired an unprecedented numbers of rounds when confronted with what they though were suicide vests.”

The belts later proved to be fake.

The police is "increasingly confident" that this attack was carried by only three individuals, he said. "We need to establish if anyone else is involved in the planning," Rowley said.

He did not disclose any of the attackers' identities.

One other person was injured by a police bullet, but the wounds were not threatening the person's life, according to Rowley.

From the 48 people hospitalized after the attack, 36 remain in hospital, and 21 of them are in critical condition, Rowley said. Seven people were killed in what the government is calling a terrorist attack on Saturday night at London Bridge and adjoining Borough Market.

"The public can expect to see additional police, both armed and unarmed, across the capital in the coming days," he said, asking people to remain calm, but vigilant, and to contact the police if they see anything suspicious.

The London Bridge area will remain closed until at least Monday morning, he said.