Father of alleged Manchester bomber Salman Abedi says his son is innocent

"It was more sophisticated than some of the attacks we've seen before, and it seems likely - possible - that he wasn't doing this on his own", Rudd said.

As of Wednesday morning, police say, they've identified all victims who lost their lives and contacted all of the families involved.

Armed and uniformed police officers stand outside a residential property near to where a man was arrested in the Chorlton area of Manchester, England, on May 23.

Though ISIS claimed responsibility for the attack, Abedi's links to the group, and whether he ever traveled to the terrorists' territory, are unclear.

Witnesses say they heard explosions as police raided a block of flats in central Manchester.

Greater Manchester Police Chief Constable Ian Hopkins said in a news conference that they believe suspected suicide bomber - 22-year-old Salman Abedi - did not act alone.

The "special relationship" between Britain and the United States was strained Thursday when UK police stopped sharing intelligence about the Manchester suicide bombing, furious that American officials had leaked key evidence related to the attack.

His family has come under scrutiny, as well: Libya's RADA counterterrorism force issued a statement on Facebook saying it has arrested and interrogated Abedi's younger brother, Hashim. The defense ministry said the changing of the guard ceremony at Buckingham Palace has been cancelled so that police officers can be redeployed elsewhere.

Britain's Queen Elizabeth speaks to Millie Robson, 15, and her mother, Marie, while on a visit to a Manchester hospital to meet victims of the terror attack.

French Interior Minister Gerard Collomb has confirmed that evil Abedi was on their radar for his suspicious activity prior to Monday's attack.

Rudd said Britain's increased official threat level will remain at "critical" as the investigation proceeds and won't be lowered until security services are convinced there is no active plot in place. Rouse said many of those hospitalized had serious wounds that would require "very long term care and support in terms of their recovery".

Asked whether the U.S. leaks had compromised the investigation, she said: "I wouldn't go that far but I can say that they are perfectly clear about the situation and that it shouldn't happen again".

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