Manchester attack: Trump condemns media leaks
They were a “grave threat to our national security”, he added, and pledged to get to the bottom of it.
His remarks come after US media published photos from the scene of Monday night’s explosion.
In Wigan, police have sealed off a street and called in a bomb disposal unit as they search a property.
The address was first raided last night, but by late afternoon, officers found “something they didn’t like” and cleared all the residents from the street, the BBC’s Danny Savage said.
A police spokesman said: “Potentially suspicious items were found at the address and a large cordon has been put in place as EOD (explosive ordnance disposal) make an assessment.”
Their searches come after Salman Abedi blew himself up at the end of an Ariana Grande concert three days ago, killing 22 people and injuring 116.
He pledged to ask the US Department of Justice to launch a review, and “if appropriate, the culprit should be prosecuted”.
“There is no relationship we cherish more than the special relationship between the US and the UK,” he added.
In a speech at the summit, Mr Trump said the attack in Manchester demonstrated the “depths of the evil we face with terrorism”.
“Innocent little girls and so many others were horribly murdered and badly injured whilst attending a concert,” he said.
“Beautiful lives with so much great potential, torn from their families for ever and ever. It was a barbaric and vicious attack upon our civilisation.
“All people who cherish life must unite in finding, exposing and removing these killers and extremists, and yes, losers, they are losers.
“Wherever they exist in our societies we must drive them out and never, ever let them back in.”
Earlier, the top US diplomat in the UK, Lewis Lukens, condemned the leaks as “reprehensible” and told the BBC action would be taken to identify those responsible.
It comes as police described the eight arrests made since the bombing as “significant”, and items seized in raids as “very important”.
Abedi detonated his “nuts-and-bolts” bomb at the end of the gig as people were making their way out of the arena.
Others were waiting in the foyer to pick up family and friends.
Security officials say they have thwarted 18 plots since 2013, including five since the Westminster attack in March.
On Wednesday, the New York Times outraged British police and government officials when it published photos appearing to show debris from the attack.
They included bloodstained fragments from the bomb and the backpack used to conceal it.
Greater Manchester Police were said to be “furious” and said they would stop sharing information with the US.
Its chief constable Ian Hopkins said the leak undermined the investigation and had distressed families “already suffering terribly with their loss”.
The New York Times newspaper has defended its decision to publish the pictures, saying they were “neither graphic nor disrespectful of victims”.
Prime Minister Theresa May has said she will make clear to US President Donald Trump that shared intelligence must remain secure when she meets him at the NATO summit.
UK officials believe that US law enforcement rather than the White House is the likely culprit for the leaks, BBC security correspondent Gordon Corera says.
Analysis: Will intelligence leaks sink the US-UK relationship?
By Anthony Zurcher, North America reporter
There may be someone in the US government who thinks these revelations could pressure the UK to take more aggressive steps of its own to address what Mr Trump in the past has termed “radical Islamic terrorism”.
Then there’s the possibility that the leaks are merely one person’s attempt to gain favour with a reporter or burnish his or her reputation as a knowledgeable insider.
If there’s one lesson to be learned from the past year, it’s there is often no need to look for complex explanations when simple individual pride or incompetence fits the bill.
Whatever the explanation, officials in both the UK and the US say the Manchester leaks are going to stop – and, given that the information is being cut off at the source, they probably will.