British officials are particularly angry that photos detailing evidence about the bomb were published in The New York Times, although it's not clear that the paper obtained the photos from U.S. officials.
British security services are also upset that Abedi's name was apparently leaked by U.S. officials while British police were withholding it -- and while raids were underway in Manchester and in Libya, where the bomber's father lives.
Hopkins, the Manchester police chief, said the leaks had "caused much distress for families that are already suffering terribly with their loss."
Trump on Thursday pledged to "get to the bottom" of leaks of sensitive information, calling the leaks "deeply troubling." He said he is asking the Justice Department and other agencies to "launch a complete review of this matter."
The New York Times defended its publication of crime-scene photographs, saying its coverage had been "both comprehensive and responsible."
"The images and information presented were neither graphic nor disrespectful of victims, and consistent with the common line of reporting on weapons used in horrific crimes," the paper said.
May said the national threat level from terrorism remains at critical -- the highest level, meaning that another attack may be imminent. Hundreds of soldiers have replaced police protecting high-profile sites including Buckingham Palace and the Houses of Parliament in London.
"The public should remain vigilant," May said.
Around the country, many people fell silent and bowed their heads at 11 a.m. for a minute in tribute to the bombing victims.
In Manchester's St. Ann's Square, where a sea of floral tributes grows by the hour, a crowd sang "Don't Look Back in Anger" -- a song by the Manchester band Oasis.
Queen Elizabeth II visited Royal Manchester Children's Hospital on Thursday to talk to some of the victims, their families and medical staff.
"It's dreadful. Very wicked, to target that sort of thing," the 91-year-old monarch told 14-year-old Evie Mills and her parents.
Fifteen-year-old Millie Robson, wearing an Ariana Grande T-shirt, told the queen she had won VIP tickets to the pop star's concert. She was leaving concert when the blast struck, remembering an intense ringing but not entirely aware that she was bleeding badly from her legs.
She credited her dad's quick action in picking her up and tying off her wounds to stem the bleeding.
"I have a few like holes in my legs and stuff and I have a bit of a cut, and my arm and just a bit here, but compared to other people I'm quite lucky really," she said.
In addition to those killed, 116 people received medical treatment at Manchester hospitals for wounds from the blast. The National Health Service said 75 people had been hospitalized.
In Berlin, former U.S. President Barack Obama and German Chancellor Angela Merkel sent a message of solidarity to the Manchester bombing victims.
"(This is) a reminder that there is great danger and terrorism and people who would do great harm to others just because they're different," Obama said.
Investigators are chasing Abedi's potential links with jihadi militants in Manchester, Europe, North Africa and the Middle East. The bomber himself died in the attack.
France's interior minister says Abedi was believed to have travelled to Syria, and U.S. Rep. Mike McCaul, chairman of the House Homeland Security Committee, said he was part of "a cell of ISIS-inspired terrorists."
Investigators are trying to find whether Abedi knew several Manchester-based jihadis, including Libyan man Abdalraouf Abdallah, who was jailed in the U.K. for terror offenses, and Raphael Hostey, an IS recruiter killed in Syria.
Investigators are also looking into the Abedi family's ties in Libya. Abedi's father Ramadan was allegedly a member of the al-Qaida-backed Libyan Islamic Fighting group in the 1990s -- a claim he denies.
Manchester is home to one of Britain's largest Libyan communities. Mohammed Fadl, a community leader, said the Abedi family is well known, but Salman did not attend many gatherings.
"Very few people in the community here were close to him and therefore Salman's fanaticism wasn't something the community was aware of," he told the AP.
He said he had heard that Salman's father took his son's passport away amid concerns about his close ties to alleged extremists and criminals.
Authorities are investigating whether Abedi could have been stopped, after Libyan community members in Manchester reported concerns about his views.
Akram Ramadan said Salman Abedi had been banned from Manchester's Didsbury Mosque, one of the largest in the city.
"There was a sermon about anti-Daesh (IS) and he stood up and started calling the Imam -- `You are talking bollocks,"' Ramadan said. "And he gave a good stare, a threatening stare into the Imam's eyes ... he was banned."
Fadl, the community leader, disputed that account and the bomber's father insisted Wednesday in an interview with the AP that Salman had no links to militants, saying "we don't believe in killing innocents."
Abedi had been in Libya in the weeks before the attack, and German magazine Focus, citing unnamed federal security source, reported that he passed through Duesseldorf airport four days before the bombing.
A German security official told the AP on Thursday the report was accurate, speaking on condition of anonymity because the information hadn't been cleared for public release.
On the artistic front, Grande cancelled concerts that were to take place Thursday and Friday in London, and in several other sites in Europe. Next week's premiere of the film "The Mummy" in London was also canceled.