Police release photo, more information about Manchester bomber

British police on Saturday released surveillance-camera images of the Manchester concert bomber on the night of the attack as they appealed for more information about his final days.

Authorities said they had made major progress in unravelling the plot behind the concert bombing, but acknowledged there were still gaps in their knowledge.

Britain reduced its terrorism threat level a notch Saturday, from "critical" to "severe," yet security remained high as jittery residents tried to enjoy a long holiday weekend. Armed police officers and soldiers were deployed at soccer matches, concerts and other big events.

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Salman Abedi, a 22-year-old Briton of Libyan descent, was the bomber who died in Monday's explosion, which killed 22 others and wounded nearly 120 as crowds were leaving an Ariana Grande concert.

The photos released by police show attacker Abedi on the night of the bombing, wearing sneakers, jeans, a dark jacket and a baseball cap. The straps of a knapsack are visible on his shoulders.

Tracking Abedi's movements

Greater Manchester Police Chief Ian Hopkins and Neil Basu, the national co-ordinator of counterterrorism policing, urged people to contact police if they had information about Abedi's movements between May 18 and Monday night.

Police said they believed he had assembled his bomb in an apartment in the citycentre.

"In the past five days, we have gathered significant information about Abedi, his associates, his finances, the places he had been, how the device was built and the wider conspiracy," they said in a statement.

"Our priorities are to understand the run-up to this terrible event and to understand if more people were involved in planning this attack."

British Prime Minister Theresa May said "a significant amount of police activity" and several arrests had led to the level being lowered. But she urged Britons to remain vigilant and said soldiers would remain at high-profile sites throughout the weekend, and start reducing their presence beginning Tuesday.

A severe threat still means an attack is "highly likely," according to the scale set by Britain's Joint Terrorism Analysis Centre.

Assistant Commissioner Mark Rowley, Britain's top counterterrorism police officer, said authorities have dismantled a "large part" of the network around Abedi, who killed 22 people and wounded dozens by bombing an Ariana Grande concert Monday in Manchester.

Photo from night of concert attack

But he said there were still "gaps in our understanding" of the plot, as investigators probed Abedi's potential links to jihadis in Britain, Europe, Libya and the Middle East.

Rowley said the investigation had made "rapid progress," and police "are getting a greater understanding of the preparation of the bomb."

"There is still much more to do. There will be more arrests and there will be more searches," he said.

Two arrests Saturday

Police used an explosive device Saturday to get into a property in Manchester to arrest two men, aged 20 and 22. Investigators have searched 17 properties, including Abedi's home in south Manchester and other houses in nearby districts.

Residents were evacuated from streets in the south Manchester neighbourhood of Moss Side in what police called a precaution as one search was carried out Saturday. Photos showed an army bomb-disposal unit at the property.

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One search was at an apartment in a Manchester high-rise that British media say was rented by Abedi in the months before the attack. Mohammed El-Hudarey, a friend of the landlord, said after Abedi moved out about six weeks ago there was a strong smell of chemicals and debris, including metal rods and cut-up fabric.

"We thought he must have been a drug dealer or doing witchcraft," El-Hudarey told the BBC.

Britain's health service said Saturday that 63 people injured in the bombing remained hospitalized, 20 of them in critical condition. A total of 116 people were treated in hospitals after the bombing.

Holiday weekend

Despite the alert, police have urged people to go out and enjoy themselves over the three-day holiday weekend.

Hundreds of soldiers replaced police at high-profile sites including Buckingham Palace and Parliament, and police armed with submachine guns have been deployed in city centres, transit hubs, tourist areas and major events.

Armed police were on the streets Saturday outside London's Wembley Stadium, and security guards conducted extra bag checks, as 90,000 fans arrived for the FA Cup soccer final between Chelsea and Arsenal, one of the biggest sporting events of the year.

Before kickoff, Prince William laid a wreath in memory of the victims alongside Manchester Mayor Andy Burnham.

Manchester slowly returned to normal, though the damaged arena and adjacent Victoria train station remained closed.

Grande promised to return to "the incredibly brave city of Manchester" for a benefit concert to raise money for the bombing victims and their families.

"Our response to this violence must be to come closer together, to help each other, to love more, to sing louder and to live more kindly and generously than we did before," the American singer said. "We will not quit or operate in fear. We won't let this divide us. We won't let hate win."