MANCHESTER, England — Britain’s domestic security chief said Wednesday it was “likely” that the bomber who killed 22 people at a concert venue was not acting alone, underscoring the expanded security measures as the nation’s threat level was raised to its highest point.
Home Secretary Amber Rudd did not provide details on possible associates of the Manchester suicide bomber, Salman Abedi. But she told the BBC that security services — which had been aware of Abedi “up to a point” before the bombing — were focusing on his visits to Libya, at least one of which was very recent.
Rudd’s French counterpart, Interior Minister Gerard Collomb, told broadcaster BFMTV that Abedi — whose parents emigrated from Libya — may have also gone to Syria and had “proven” links with Islamic State, which claimed responsibility for the Manchester blast and called Abedi a “soldier.”
A series of arrests since the Monday night attack have included Abedi’s brother, police said.
On Tuesday, British Prime Minister Theresa May took Britain’s alert level from “severe” to its highest rating, “critical.” The move clears the way for thousands of British troops to take to the streets and replace police officers in guarding key sites.
May announced the move after chairing an emergency meeting of her security cabinet and concluding that Abedi may have been part of a wider network poised to strike again. The decision, she said, was “a proportionate and sensible response to the threat that our security experts judge we face.”
On Wednesday, British Parliament announced that “due to the raised national security threat” all public tours would be stopped, with immediate effect. The Changing the Guard ceremony at Buckingham Palace — a popular tourist attraction — was also canceled.
And in a highly unusual public rebuke, Rudd slapped down U.S. authorities for leaking information about the investigation.
Some details about the case — including the suspect’s name — first appeared in the U.S. media.
When asked by the BBC if she would look again at information sharing with other countries, she said: “Yes, quite frankly. The British police have been very clear that they want to control the flow of information in order to protect operational integrity, the element of surprise.”
She said that it was “irritating if it gets released from other sources and I have been very clear with our friends that should not happen again.”
The worst terrorist attack on British soil in more than a decade was carried out by a British-born son of Libyan immigrants who was born and raised a short drive from the concert hall that he transformed from a scene of youthful celebration into a tableau of horror.
Health officials said Wednesday that in addition to the dead, 20 people remained in “critical care” and were suffering from “horrific injuries.”
The attack, which came at the close of a concert in the northern English city by American pop star Ariana Grande, was claimed Tuesday by the Islamic State, saying one of its “soldiers” was responsible.
Even as officials and experts cast doubt on the terrorist group’s assertion, however, authorities were scrambling to execute searches, arrest potential accomplices and reinforce security systems at a spectrum of public events that look newly vulnerable to attacks like Monday’s.
After years of successfully fending off more-sophisticated strikes even as countries across continental Europe have fallen victim to bombings, Monday night’s carnage underscored that Britain is not immune amid a rising tide of extremist violence.
The highest priority for police, said Greater Manchester Chief Constable Ian Hopkins, was to “establish whether [Abedi] was acting alone or as part of a network.”
Earlier he had said that Abedi executed the bombing alone and that he “was carrying an improvised explosive device, which he detonated, causing this atrocity.”
But unlike in previous high-profile attacks — including one in March in which an assailant driving a speeding car ran down pedestrians on a London bridge, then stabbed to death a British police officer — experts said it was unlikely that Monday’s attack had been carried out without help.
“Getting a car or a knife is easy,” said Raffaello Pantucci, a terrorism expert at the London-based Royal United Services Institute. “Making a bomb that works and goes off when you want it to go off takes preparation and practice. And it usually involves other people.”
Pantucci said British authorities “are going to try to figure out who [Abedi] knows, who he’s linked to. Did he build the bomb itself, or did someone build it and give it to him?”
If police have an answer, they did not say so publicly Tuesday. But there was ample evidence of a widening security operation, with the arrest of a 23-year-old from south Manchester in connection with the bombing. Police also carried out searches at two homes, including the house in the leafy suburban neighborhood where Abedi, 22, was registered as having lived.
A family friend said Abedi traveled frequently between Libya and Britain. “We have an Daesh problem in Libya. We wonder whether he met people there who trained him,” said the friend, who spoke on the condition of anonymity. Daesh is the Arabic acronym for the Islamic State.
Even before May’s announcement of a “critical” threat level for just the third time ever — the first two came in 2006 and 2007 — authorities from London to Scotland said that they would be reviewing security plans for upcoming public events. Even smaller gatherings that would not have been policed in the past may now get protection, they said.
“Over the coming days as you go to a music venue, go shopping, travel to work or head off to the fantastic sporting events, you will see more officers, including armed officers,” said Commander Jane Connors of London’s Metropolitan Police Department.
May’s decision to deploy the military means the public may now see soldiers rather than police. May said the military would operate under police command.
The escalation came as the nation grieved for the young victims, with thousands of people converging on Manchester’s graceful Albert Square for a vigil that was part solemn remembrance and part rally against extremism.
To roaring applause, Manchester Mayor Andy Burnham vowed that the city — which has seen hardship, having been bombed relentlessly during World War II — would not succumb to division or anger. A poet named Tony Walsh delivered an ode to the city titled “This Is the Place.” And in what has become a dark mainstay of life in Western Europe, passersby left candles, flowers and cards for the dead.
The casualties included children as young as elementary school students. Police said that among the 59 people injured, a dozen were younger than 16.
Among the dead was Saffie Rose Roussos, who was just 8 years-old. The first victim to be publicly identified was Georgina Callander, an 18-year-old student.
Other names were being released Wednesday. By midmorning, nine people had been named among the dead.
In a speech outside 10 Downing Street, where flags were lowered to half-staff, May called the Manchester killings a “callous terrorist attack.”
“This attack stands out for its appalling, sickening cowardice deliberately targeting innocent, defenseless children and young people who should have been enjoying one of the most memorable nights of their lives,” she said.
May later visited Manchester, meeting with local authorities and signing a condolence book honoring the victims.
Queen Elizabeth II, meanwhile, led guests of a garden party at Buckingham Palace in a moment of silence and issued a statement expressing her “deepest sympathies.”
“The whole nation has been shocked by the death and injury in Manchester last night of so many people, adults and children, who had just been enjoying a concert,” she said.
The Monday night attack was the worst terrorist strike on British soil since 2005, when Islamist extremists bombed the London subway and a bus, killing 54 people.
Pantucci, the security expert, said that authorities had disrupted several plots in recent months but that Monday’s attack somehow slipped through. Understanding why, he said, will be crucial.
“They’ve been dealing with a very high threat tempo,” he said. “But this is one they weren’t able to stop.”
Adam reported from London. Isaac Stanley-Becker, James McAuley and Rick Noack in Manchester; Paul Schemm in Addis Ababa, Ethiopia; and Devlin Barrett, Brian Murphy and Ellen Nakashima in Washington contributed to this report.