Britain's MI5 intelligence service has launched an internal probe into whether vital clues were missed ahead of the Manchester attack, as the city marked on Monday a week since the carnage that claimed 22 lives. Manchester City Council called a vigil in the centre of the northwest English city at 2131 GMT - the exact moment that 22-year-old Salman Abedi detonated his bomb outside a pop concert by teen idol Ariana Grande in one of Europe's biggest indoor arenas.
The names of the victims, including six children, were read out in front of the city's town hall earlier on Monday in front of hundreds of people at an annual religious ceremony. A nearby square that has been the focus of remembrance was packed with floral tributes and heart-shaped balloons, as well as runners' bibs left by participants in a half-marathon on Sunday.
"You tried to destroy us but you've brought us closer together," read one message of defiance. Investigators meanwhile pushed ahead with their probe of the attack, which was claimed by the Islamic State group. Authorities arrested a 23-year-old man in the southern coastal town of Shoreham-by-Sea, more than 400 kilometres (250 miles) from Manchester.
That brings the total number of people now detained on UK soil to 14, all of them men, while Abedi's father and brother have been held in Libya, where officials said the two brothers were IS jihadists. MI5 are also looking at decisions taken in the case of Abedi, who used to be on a terror watchlist but was no longer on it at the time of the attack, and whether warnings about his behaviour were ignored amid mounting criticism of the security services.
"There is a lot of information coming out at the moment about what happened, how this occurred, what people might or might not have known," interior minister Amber Rudd told Sky News. "It is right that MI5 take a look to find out what the facts are," she said, adding: "We shouldn't rush to make any conclusions at this stage".
Two people who knew Abedi made separate calls to an anti-terrorism hotline to warn the police about his extremist views, British media have reported.
The Mail on Sunday also cited a source saying US federal agents had been investigating Abedi since the middle of 2016 and had flagged up concerns to MI5. The BBC reported that Abedi had taken part in the armed uprising against Libyan dictator Moamer Kadhafi's regime as a teenager during school holidays. British investigators have released pictures of Abedi taken from CCTV shortly on the night of the massacre, appealing to the public for help in tracing his movements in the days before.
Abedi could be seen wearing jeans and trainers, a black bodywarmer and a baseball cap, with the straps of the backpack believed to contain the bomb visible on his shoulders. The police statement said one of the last places he went to before the attack at the Manchester Arena venue was a city centre flat, where they believe he may have finished assembling the device. None of the men arrested have been charged with a crime yet and police have up to 14 days in which to do so under special anti-terrorism laws.
Britain's Prime Minister Theresa May on Saturday lowered the terror threat level, which had been hiked in the immediate aftermath of Monday's attack. Operation Temperer, which involved the highly unusual deployment of armed troops on Britain's streets, will also be wound down on Monday night. In another sign of a lowering of security tensions, Victoria Station in Manchester, a major transport hub which was next to the blast site and has been shut since the tragedy, is due to reopen on Tuesday.
Investigators said they have a 1,000-strong team working on the probe and have significant details on Abedi's associates and movements, his finances, and how the bomb was built. But cuts in police force numbers made while May was interior minister have become a focus for the campaign ahead of a general election on June 8 and polls have shown her strong lead against the Labour Party's Jeremy Corbyn shrinking in recent days.
From 2009 to 2016, the number of police officers fell by almost 20,000, or around 14 percent. May argues that the government has increased funding for security and intelligence agencies. Authorities are currently handling 500 terror-related investigations into 3,000 individuals, with another 20,000 people on the radar posing a "residual risk". The bombing was the latest in a series of IS-claimed attacks in Europe that have coincided with a US-led offensive against the jihadist group in Syria and Iraq by countries including Britain.