LONDON — The mayor of London accused the government on Monday of failing to give judges the tools they need to keep people who pose terrorist threats in prison, a day after a man who had recently been released went on a stabbing rampage in South London.
The attacker, who wounded three people on Sunday before being shot and killed by the police, was identified by the police as Sudesh Amman, a 20-year-old from London who was jailed in 2018 for terrorism-related offenses. He was sentenced to more than three years in prison, but his early release came automatically, in line with government policy.
The mayor, Sadiq Khan, said he was “angry” about the government’s handling of the situation, noting that London has experienced two attacks in the past three months that were carried out by men convicted of terrorism-related offenses who had been recently released.
On Monday, the Islamic State claimed responsibility for the attack on the Hoop messaging app, saying the attacker was one of its “fighters.” The group has been using the messaging app since the authorities began a sustained effort to dislodge the group from Telegram, which had been their principal communication method since late 2014.
Mr. Amman was wearing a fake explosive device, a tactic that has been used in several recent attacks, including others claimed by the Islamic State. It is unclear what involvement, if any, the group had in Sunday’s attack.
London has been the site of several deadly terrorist attacks in the past few years, and each one has renewed questions about whether Britain’s approach to the threat is sufficient.
“There’s lots of questions I’ve got for the government in relation to what they are doing to keep us safe,” Mr. Khan said in an interview with Sky News, warning that not enough was being done to prevent people convicted of terrorist offenses from carrying out attacks.
“What are the government doing to make sure they are not a danger to the public?” asked Mr. Khan, who is a member of the opposition Labour Party. He pointed to revisions in the law that prevented judges from issuing indeterminate sentences to protect the public.
Mr. Amman was released in January, having been convicted in May 2018 under the Terrorism Act. He was first arrested on suspicion of planning a terrorist attack, but was ultimately charged with ownership and distribution of terrorist propaganda and instructional manuals. There were 224 people in custody in Britain on terrorism-related offenses as of September, the latest figures from the government.
On Sunday, Mr. Amman was being followed on foot by armed officers — a rarity in Britain, where police are often unarmed — who were part of a counterterrorism surveillance operation.
He had been sentenced to 16 years in prison for his involvement in a bomb plot but was released after eight. He appeared to have been released automatically “on license” — meaning under certain conditions — according to the parole board, which did not review his case before his release.
Mr. Khan was taking part in a prison rehabilitation conference near London Bridge when he stabbed several people and fled before he was shot and killed by the police. Like Mr. Amman, he was also wearing a fake explosive vest.
Prime Minister Boris Johnson, in a speech in London on Monday, thanked the police for their swift response and said it was “time to take action” to ensure people convicted of terror offenses do not qualify automatically for early release.
“We’re bringing forward legislation to stop the system of automatic early release,” he said, adding that the difficult part is figuring out “how to apply that retrospectively to the cohort of people who currently qualify.”
After the December attack, Mr. Johnson vowed that 74 people who had been jailed for terrorism offenses and released early would have the conditions of their release reviewed, and last month the government announced plans to toughen terrorism sentences and end early releases. But the new measures apply only to the most serious and violent offenders — Mr. Amman is not among them.
Mr. Amman was charged in 2018 with disseminating terrorist material and collecting information useful for terrorist attacks, after the police were alerted to his messages in the Telegram app that showed support for the Islamic State. His mother told Sky News on Monday that he was radicalized online and in prison.
When Mr. Amman was sentenced, Acting Commander Alexis Boon, head of London’s Metropolitan Police Counterterrorism Command, said the police had “recovered a plethora of evidence which not only proved Amman’s criminality but demonstrated the worrying extent of his terrorist mind set,” according to The Independent.
A BBC reporter recalled how Mr. Amman had smiled in court at the time of his sentencing.
The police said on Monday that two residential properties — one in South London and another in Bishop’s Stortford, about 30 miles north of the capital — had been searched, but that no arrests had been made.
In his interview with Sky News, Mr. Khan noted that prisons were stretched to the limit and that probation services were struggling to cope with the number of released offenders.
“We’ve got roughly speaking 200-plus people convicted of terrorism in prisons now,” Mr. Khan said. “What are we doing to make sure they are being punished and reformed, rather than radicalized?”
Some ex-officials made the case on Monday for some terrorism convicts to be given indefinite sentences, even as they stressed the need for better rehabilitation services.
But analysts questioned how a prison service that is already overburdened, especially after cuts made during the Conservatives’ decade-long austerity policies, would cope with extended sentences. The policy of automatically releasing some prisoners halfway into their sentences was originally intended to control a booming prison population.
The government seemed poised on Monday to announce a broader crackdown on early releases.
Sir Mark Rowley, the former head of British counterterrorism policing, suggested on BBC Radio 4 that the government should pair indeterminate sentences with better de-radicalization programs.
“If someone is clearly driven by an ideology and they believe that slaughtering other people is a sort of God-given purpose, then I can see a case for that,” Mr. Rowley said. “As long as we put alongside it the rehabilitation and de-radicalization programs to give someone the opportunity to change their ways and be released.”
But others questioned whether the prison service was sufficiently equipped to hold terrorism convicts and prepare them for release.
“I am more concerned about what happened when he was in custody,” said Ian Acheson, who led a review of Islamist extremism in prisons and the probation service several years ago. “I am still unconvinced that the prison service itself has the aptitude or the attitude to assertively manage terrorist offenders.”
Rukmini Callimachi contributed reporting.