Police said the nine men in British custody ranged in age from 18 to 44, including a 30-year-old arrested in the Moss Side area of south Manchester early Friday and a 44-year-old detained in nearby Rusholme later in the day.

"I woke up because I heard the police shouting, they were shouting 'Get down, it's the police, hands on the ground, get on the ground'," said local resident Anita Santonelli, who said she saw around 10 armed police officers during the morning operation.

Opposition Labour leader Jeremy Corbyn said it was the "responsibility" of governments to minimise the risk of terror by giving police the funding they need after cuts made while Conservative Prime Minister Theresa May served as interior minister.

Following Monday's attack in which 116 people were also injured, May and Corbyn suspended campaigning for a snap June 8 election.

US 'full responsibility'

The United States' top diplomat Rex Tillerson also visited London on Friday in an expression of solidarity after Britain reacted furiously to leaks of sensitive details about the investigation emanating from Washington.

"We take full responsibility for that and obviously regret that that happened," the secretary of state told reporters.

Britain briefly suspended intelligence-sharing with the United States over the leaks, but Tillerson said their "special relationship" would "withstand this particular unfortunate event".

President Donald Trump has threatened to prosecute those responsible for the "deeply troubling" security breach.

'Critical' threat

Monday's bombing at a concert by US pop idol Ariana Grande was the latest in a series of IS-claimed attacks in Europe that have coincided with an offensive on the jihadist group in Syria and Iraq by US, British and other Western forces.

Dozens of IS fighters were killed in US strikes on Syria Friday, while masked gunmen killed at leat 28 people in an attack on Coptic Christians in Egypt.

Britain's terror threat assessment has been hiked to "critical", the highest level, meaning an attack is considered imminent.

With the heightened security threat, Chelsea have cancelled Sunday's parade in London to celebrate their Premier League football title, saying they thought it was "inappropriate to go ahead" following the bombing.

Arsenal, who face Chelsea in Saturday's FA Cup final, have also said they will not hold a victory parade if they win at Wembley.

The issue of security, which was not widely discussed in the general election campaign before the attack, is now expected to feature highly.

A YouGov poll in The Times newspaper put the Conservatives on 43 percent compared to Labour on 38 percent, far better for Labour than the double-digit margin that had previously separated it from the governing party.

However, the poll also suggested that 41 percent of respondents believe the Conservatives would handle defence and security best, compared to 18 percent who said the same of Labour.

YouGov polled 2,052 people on Wednesday and Thursday.

Hunting accomplices

May was at the G7 summit in Sicily on Friday where she got the group to demand action from internet providers and social media firms against extremist content online.

"The fight is moving from the battlefield to the internet," she told the G7.

She faced questions from British journalists over police funding cuts during her six years as the interior minister.

The number of police officers fell by 14 percent, or almost 20,000, between

2009 and 2016, according to the independent Institute for Fiscal Studies think tank.

"We have protected counter-terrorism police funding, we've increased the funding for our security and intelligence agencies and we continue to provide them with the support they need," she insisted.

Manchester-born Abedi, a university dropout, grew up in a Libyan family in the northwestern English city.

Libyan officials said he and his brother Hashem belonged to IS, while their father Ramadan once belonged to a now-disbanded militant group with alleged ties to Al-Qaeda.

A British official said that Abedi had been on the periphery of the intelligence radar before the massacre.

Manchester defiant

Grande said Friday she was planning a charity concert in the city, writing on social media that she wanted to give "an expression of love for Manchester".

On Friday evening, the city hosted an athletics contest, the Great City Games, in which the likes of former world 100 metres champion Kim Collins competed amid robust security.

Victims Alison Howe, 45, and Lisa Lees, 47, were honoured Friday by a vigil in their home town of Oldham, east of Manchester.

Hundreds of people gathered in the Tandle Hill Country Park, releasing pink helium balloons and laying flowers.

"The memory of our victims and their bravery will be known in all of our hearts. We are Manchester, and we stand together," said speaker Elisia Smith, 24.

Tattoo artists in Manchester have reported a rush of people seeking inkings of worker bees, a longstanding symbol of the industrious city.

Some 66 people are still being treated in hospital, including 23 in critical condition, medical officials said.

Twelve of those injured were under 16, and the youngest killed was an eight-year-old girl.