LONDON/MANCHESTER (REUTERS, AFP) - British Prime Minister Theresa May said on Thursday (May 25) she would tell United States President Donald Trump that intelligence shared between their two countries had to remain secure after leaks to US media about the Manchester attack.

British police stopped sharing information about the suicide bombing with the US, a British counter-terrorism source told Reuters earlier, after police chiefs said the leaks to media risked hindering their investigation.

May said she would talk to Trump at a Nato summit later on Thursday about the leaks, which included the publication of photographs of the bomb site by the New York Times.

"On the issue of the intelligence sharing with the United States of America, we have a special relationship with the USA. It is our deepest defence and security partnership," May told reporters as she arrived at the summit. "Of course that partnership is built on trust and part of that trust is knowing that intelligence can be shared confidently, and I will be making clear to President Trump today that intelligence that is shared between law enforcement agencies must remain secure."

In a statement in Brussels, Trump slammed the alleged US intelligence leaks, calling the leaks a "grave threat to our national security". He vowed to bring anyone caught leaking US intelligence to justice. "The alleged leaks coming out of government agencies are deeply troubling," Trump said in the statement. "I am asking the Department of Justice and other relevant agencies to launch a complete review of this matter, and if appropriate, the culprit should be prosecuted to the fullest extent of the law."

British police were on Thursday hunting for a network linked to the suicide bomber, Salman Abedi, after he detonated a sophisticated device at a concert venue packed with children on Monday night, killing 22 people.

A source with knowledge of the investigation told Reuters that the attacker, British-born Salman Abedi, may have made the bomb himself or with some assistance from an accomplice. "The focus is still the search for accomplices and the network but he could have made this bomb himself," the source told Reuters.

The source added that while the 22-year-old bomber may have had some assistance, it was also possible that he made the bomb himself. Some investigators had feared that an experienced bomb-maker was still at large.

British police, who are holding eight people in custody, said Thursday they had made significant arrests and had uncovered important items in their investigation. "I want to reassure people that the arrests that we have made are significant, and initial searches of premises have revealed items that we believe are very important to the investigation," police chief Ian Hopkins told reporters. "These searches will take several days to complete."

Britain's decision to stop sharing police information with US agencies was an extraordinary step as Britain sees the United States as its closest ally on security and intelligence.

"This is until such time as we have assurances that no further unauthorised disclosures will occur," said the counter-terrorism source, who spoke on condition of anonymity.

Many European cities, including Paris, Berlin and Brussels, have suffered attacks in the last two years, underlining the importance of confidential intelligence cooperation.

Trump was widely criticised this month after it emerged he had discussed sensitive Syria-related intelligence, originating from an ally, with Russian officials at a White House meeting. May said at the time Britain would continue to share intelligence with Washington.

The official threat level in Britain was raised after the Manchester attack to "critical", its highest level, meaning a further attack could be imminent. Troops have been deployed to free up police officers for patrols and investigations.

FALSE ALARMS

England's National Health Service said a total of 116 had been injured in the attack, with 75 admitted to hospital. Twenty-three remained under close care.

Soldiers and bomb disposal experts rushed to a street in the south of the city after a call to police, but it turned out to be a false alarm.

In London, commuters were briefly evacuated from the Victoria Station on Thursday after a fire alarm went off in another security scare.

Queen Elizabeth visited the Royal Manchester Children's Hospital, where some of the casualties have been treated.

A minute's silence was observed in honour of the victims at a square in central Manchester and in other places in Britain.

The bombing, which took place at the Manchester Arena indoor venue just after the end of a concert by US pop singer Ariana Grande, was the deadliest in Britain since July 2005, when 52 people were killed in attacks on London's transport network.

The Manchester attack has caused revulsion across the world because it targeted children and teenagers, who make up the bulk of Grande's fan base.

The victims range from an eight-year-old schoolgirl to parents who had come to pick up their children.

FAMILY IN FOCUS

A total of 11 people have been arrested in Britain and Libya over the bombing since Tuesday, including Abedi's father and brother in Libya.

A Libyan security source told the AFP news agency Thursday that Abedi's father was once part of a Libyan militant group with alleged ties to the Al-Qaeda militant group. Ahmed bin Salem, spokesman for Libya's Deterrence Force which acts as the police for Libya's unity government, said Abedi's father "was a member of the Libyan Islamic Fighting Group".

Libyan authorities have said Abedi's brother had been aware of the attack plan. The country said Thursday it was working 'closely' with Britain on the attack probe.

Separately, a source close to Abedi's family in Libya said the attacker had expressed a desire to avenge the killing of a friend in the British city last year. His friend, also of Libyan descent, died after being stabbed by British youths in Manchester in May 2016, the source said on condition of anonymity.

Abedi had also reportedly called his mother just before the vile attack, according to BBC Newsnight. The programme cited a Libyan security source as saying he had called his brother in Libya to ask him to tell their mother Samia Tabbal to return his call. Tabbal is said to be a nuclear science engineer who graduated top of her class from Tripoli University.

"I am sure Salman's mother and father are very shocked by what he did," a close friend of the family told The Daily Mail.

Eight men remain in custody in Britain, most arrested in and around Manchester, including three men near the house where Abedi lived.

British media indicated a 23-year-old man arrested Tuesday is likely to be Abedi's older brother Ismael.

A woman arrested Wednesday was released a few hours later without charge.

Manchester's police chief said on Wednesday they believed Abedi was part of a terror network.

Police chiefs have made clear they are furious about the publication of confidential material in US media, including bomb site photographs in the New York Times, saying such leaks undermined relationships with trusted security allies.

"This damage is even greater when it involves unauthorised disclosure of potential evidence in the middle of a major counter-terrorism investigation," a National Counter Terrorism Policing spokesman said in a statement.

Britain routinely shares intelligence with the United States bilaterally, and also as part of the "Five Eyes" network which also includes Australia, Canada and New Zealand.

CRIME SCENE PICTURES

The pictures published by the New York Times included remains of the bomb and of the rucksack carried by the suicide bomber, and showed blood stains amid the wreckage.

"I think it's pretty disgusting," said Scott Lightfoot, a Manchester resident, speaking outside a train station in the city. He criticised media for publishing such material. "Who's leaking it? Where's it coming from? This is British intelligence at the end of the day, people shouldn't be finding out about this."

The Financial Times reported that such images are available across a restricted-access encrypted special international database used by government ordnance and explosives experts in about 20 countries allied with Britain. It said the database was built around a longstanding US-British system.

The BBC said Manchester police hoped to resume normal intelligence relationships soon but were furious about the leaks.

US channel ABC News reported that police had found a kind of bomb-making workshop in Abedi's home and he had apparently stockpiled enough chemicals to make additional bombs.

British news website The Independent also reported bomb-making materials which could be primed for imminent attacks had been found in the raids following the Manchester bombing. The report said one suspect device was blown up in a controlled explosion.