UK security officials have angrily condemned the US leaking of images appearing to show the blood-stained remnants of the Manchester suicide bomber's detonator and backpack.
The pictures, published in the New York Times to the consternation of British officials, show torn scraps from a blue Karrimor rucksack along with screws and nuts after the Manchester Arena blast.
A National Counter Terrorism Policing spokesperson said the leaking "undermines our investigations and the confidence of victims".
"This damage is even greater when it involves unauthorised disclosure of potential evidence in the middle of a major counter terrorism investigation," a spokesperson said.
The unauthorised publishing comes barely hours after Home Secretary Amber Rudd warned US authorities not to let slip details of the terror investigation, having already released the identity of bomber Salman Abedi ahead of UK police.
The New York Times described the collection of eight photographs as "law enforcement images" without detailing how the newspaper received them.
The presence of a ruler alongside the suspected detonator makes it clear the images were taken by investigators rather than members of the public in the wake of Monday night's explosion.
ITV News Political Correspondent Carl Dinnen said Prime Minister Theresa May is expected to raise the matter with US President Donald Trump at a Nato summit on Thursday with it causing "cold fury" in Whitehall.
A Whitehall source condemned the leak, telling ITV News: "These images will be distressing to victims, their families and the wider public.
"British officials and ministers are making it clear to their US counterparts that these leaks from within the system are totally unacceptable."
Dinnen said: "That is quite extraordinary language for these sort of people to be using about Britain's closest ally, especially in intelligence terms."
The Home Office declined to comment on the leak, which is expected to lead to disquiet between Britain and its traditionally closest intelligence ally.
Ms Rudd earlier told ITV News that British officials had spoken to their allies and she was confident they would "take steps" to ensure further information leaks were not repeated after the release of bomber Abedi's identity.
She confirmed she has contacted US officials to make her "irritation clear" at information coming out from America.
Information is routinely shared by British and US security and intelligence agencies as part of the special relationship.
Surveillance information is also shared between the nations as part of the Five Eyes arrangement with Canada, Australia and New Zealand.
Condemning the latest leak, the National Counter Terrorism Policing spokesperson said: "We greatly value the important relationships we have with our trusted intelligence, law enforcement and security partners around the world.
"These relationships enable us to collaborate and share privileged and sensitive information that allows us to defeat terrorism and protect the public at home and abroad.
"When that trust is breached it undermines these relationships, and undermines our investigations and the confidence of victims, witnesses and their families.
"This damage is even greater when it involves unauthorised disclosure of potential evidence in the middle of a major counter terrorism investigation."