The medical director for the NHS in London, Dr Vin Diwakar, said on Sunday that one of the three people injured in the attack had been allowed to return home while the other two remain in a stable condition in hospital. The group via its propaganda Amaq news agency said on Saturday that the attack was carried out by "a fighter from the Islamic State", according to the site intelligence group, which monitors jihadist activities.
London Mayor Sadiq Khan said the bystanders who brought down the attacker could have followed advice and run away for their own safety but made a decision to run toward danger instead.
The argument centers over the early release from prison of Usman Khan, who served roughly half his sentence before being set free.
In 2012, he was sentenced to indeterminate detention for "public protection" with a minimum jail term of eight years after pleading guilty to preparing terrorist acts.
Britain's political leaders are sparring over who is responsible for the early release of a convicted man who launched a stabbing attack in central London that left two dead.
Police have arrested a man in Stoke-on-Trent on suspicion of preparing a terrorism attack.
Corbyn, a veteran peace campaigner, said he believed convicted terrorists should "not necessarily" serve their full prison terms, suggesting it would depend on the nature of their sentence and also how they had behaved in prison.
Mr Johnson said Khan was under "various conditions", adding: "He had mentors, he had restrictions on his mobile phone, he had restrictions on internet access".
"We saw Londoners, ordinary citizens, acting in an extraordinary way", he said.
He added that there were 74 other convicted terrorists now on the streets who have also been released early, and he promised to toughen their monitoring.
British media reported that Lukasz, who works as a chef, snatched a 1.5 meter (5 foot) narwhal (whale) tusk from the wall of the United Kingdom capital's Fishmongers' Hall as Friday's stabbing attack unfolded.
"I think it's fair to say we're all shocked and saddened", the minister said.
Tour guide Stevie Hurst told BBC radio that "everyone was just on top of him trying to bundle him to the ground". Another man was seen walking away from the incident holding a knife that was retrieved from the scene.
Attention has swiftly turned to how Khan could have been released from prison after serving less than seven years of his sentence.
Inmates are usually released half-way through this type of determinate sentence - and time spent in custody before trial may have been taken into account.
In a campaign speech delivered in Yorkshire, Corbyn said he did not want to have knee jerk legislation to react to an atrocity, but wanted information about exactly what happened in prison with the London Bridge attacker.
Judges then said it was up to the Parole Board to decide when the men were safe to be released from jail.