MANCHESTER, England — The police chief leading the investigation into a suicide bombing that killed 22 people at a Manchester concert said Wednesday that the attacker had not acted alone and authorities were trying to unravel a wider web of plotters.
“It’s very clear that this is a network we are investigating,” said Greater Manchester Chief Constable Ian Hopkins.
Hopkins said police had taken at least four people into custody, including the bomber’s brother, in connection with the attack since Monday night. Raids continued Wednesday, including one in the heart of Manchester.
The comments — which came as British troops fanned out across London, including in front of 10 Downing Street — confirmed what other senior British officials have hinted.
Britain’s domestic security chief, Home Secretary Amber Rudd, said earlier it was “likely” that the bomber was part of a larger plot, underscoring the need for expanded security measures as the nation’s threat level was raised to its highest point.
Rudd did not provide details on possible associates of the Manchester suicide bomber, Salman Abedi, a British-born citizen whose parents emigrated from Libya. 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 may have also gone to Syria and had “proven” links with the Islamic State, which claimed responsibility for the Manchester blast and called Abedi a “soldier.”
Abedi’s father, Ramadan Abedi, said his son sounded “normal” when they last spoke five days ago. The elder Abedi told the Associated Press by telephone from Tripoli, Libya, that his son planned to visit Saudi Arabia and then spend the Islamic holy month of Ramadan with family in Libya.
“We don’t believe in killing innocents,” he told the AP. “This is not us.”
On Tuesday, British Prime Minister Theresa May took Britain’s alert level from “severe” to its highest rating, “critical.” The decision, she said, was “a proportionate and sensible response to the threat that our security experts judge we face.”
The impact was quick and visible.
In London, nearly 1,000 soldiers were deployed onto the streets to help free up police. Soldiers were seen at prominent locations including Downing Street and Buckingham Palace.
The mayor of London, Sadiq Khan, warned Londoners that they will “see officers who are carrying firearms and they will see military personnel.” He then tried to reassure the public: “No reason at all to be panicked, no reason to be alarmed.”
The British Parliament announced that “due to the raised national security threat” all public tours of the Palace of Westminster would be stopped. The Changing of the Guard ceremony at Buckingham Palace — a popular tourist attraction — was also canceled.
Chelsea, the title-winning soccer club in England’s Premier League, called off a planned victory parade through London in an open-top bus. A team statement that it “would not want in any way to divert important resources.”
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 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, which said 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 was 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 a 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 an Arabic acronym for the Islamic State.
Even before May’s announcement of a “critical” threat level for just the third time — the first two came in 2006 and 2007 — authorities from London to Scotland said 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.
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.