Donald Trump Thursday slammed as "deeply troubling" USA leaks on the probe into the Manchester suicide bombing, warning those responsible could face prosecution.
May said Thursday morning she would "make clear" to Trump during their meeting at the North Atlantic Treaty Organisation summit that "intelligence that is shared between our law enforcement agencies must remain secure".
In a statement issued by the White House, the U.S. president said he had ordered the Department of Justice and other agencies to launch a full review of leaks he described as "a grave threat to our national security". Questioned about Mr Trump's apparent leaking to the Kremlin, Ms May had said: "We continue to work with the United States and we continue to share intelligence with the United States, as we do with others around the world".
This is a breaking news story.
Editor's Remarks: Theresa May has been left scratching her head after USA officials released the name of the Manchester bomber before United Kingdom authorities, and classified crime scene photos were published by the New York Times.
"These leaks have been going on for a long time and my Administration will get to the bottom of this", Trump said.
And since Trump took office, he and other Republicans have repeatedly expressed frustration with leaks within the US intelligence community, particularly of damaging information about Trump and his associates.
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The British home secretary, Amber Rudd, called them "irritating".
A spokesman for Britain's anti-terrorism police said investigators relied on trust with its allies, adding: "When that trust is breached it undermines these relationships and undermines our investigations".
"Last night family-liaison officers shared with those families the fact that intelligence had been leaked and published in The New York Times", he said.
Greater Manchester Mayor Andy Burnham later confirmed the report, telling CNN that, "we quite frankly can't risk it anymore". When that trust is breached it undermines these relationships, and undermines our investigations and the confidence of victims, witnesses and their families.
Without an election in the offing - Britons go to the polls June 8 - some politicians may have voiced their frustration "behind closed doors", he said. "Let me just say in the strongest possible terms that we condemn them and we are determined to investigate and to bring appropriate action". "We are determined to identify these leaks and to stop them".
Trump was widely criticized this month after it emerged he had discussed sensitive Syria-related intelligence, originating from an ally, with Russian officials at a White House meeting.
"We are furious. This is completely unacceptable", a government ministry source said of the images "leaked from inside the U.S. system".