British-born Salman Abedi, 22, who was known to security services, killed 22 people and injured 64 others at a concert venue packed with children on Monday.
Images obtained by The New York Times newspaper showed a detonator that bomber Salman Abedi was said to have carried in his left hand, shrapnel including nuts and screws, and the shredded remains of a blue backpack.
"Three men have been arrested after police executed warrants in South Manchester in connection with the ongoing investigation into Monday night's horrific attack at the Manchester Arena", a Greater Manchester Police statement said.
Britain's Daily Telegraph reports in the USA that officials with access to the shared Five Eyes intelligence "were openly briefing the media on what they had been told about Abedi and his "cell of Isis-inspired terrorists".
A source said British investigators were hunting for anyone who may have helped build the suicide bomb.
British officials said Abedi had been on the radar of the intelligence community before the massacre.
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"I think it's pretty disgusting", said Scott Lightfoot, a Manchester resident, speaking outside a train station in the city.
Manchester's mayor Andy Burnham said he has contacted the US ambassador to the United Kingdom over the leaks to the media from the investigation into Monday's terrorist attack.
The prime minister will say she is "grateful for the support and solidarity shown by all our North Atlantic Treaty Organisation allies" and point to the bombing as an example of why the global community must do more to tackle terrorism. A woman detained on Wednesday was released without charges.
British media have reported that one of the eight people under arrest is Abedi's brother but police have not confirmed that.
The arrest was made following searches at an address in the town of Nuneaton in central England, and is the first outside the Manchester area.
French Interior Minister Gerard Collomb said Abedi had "likely" been to Syria after the trip to Libya, citing information provided by British intelligence services to their counterparts in Paris.
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The government said almost 1,000 soldiers were deployed Wednesday instead of police in high-profile sites in London and elsewhere. He said he spoke to his son five days ago and that he was getting ready for a religious pilgrimage to Saudi Arabia.
The official spoke on condition of anonymity because he was not authorized to speak publicly.
US media outlets released the initial death toll and details about the attack before British police released the information to the United Kingdom media.
But, hours after the warning, the New York Times published the detailed photographs.
A government source told the Guardian newspaper, "Protests have been lodged at every relevant level between the British authorities and our United States counterparts".
British Prime Minister Theresa May will raise the issue with US President Donald Trump when she meets him at a North Atlantic Treaty Organisation summit in Brussels later on Thursday, a government source told Reuters. The terror attack had already led to the UK's political parties suspending general election campaigning, with polling day just over two weeks away on June 8.
British officials are particularly angry that photos detailing evidence about the bomb used in the Manchester attack were published in The New York Times, although it is not clear that the paper obtained the photos from US officials.
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Then-National Security Adviser Michael Flynn speaks during the daily news briefing at the White House in Washington, Feb. 1, 2017. Opening himself up to questioning from Senate investigations would be risky for Flynn given his current legal troubles.