Part of that threat assessment is the fear that Abedi, who blew himself up in the bomb attack, could have been working as part of a group with possible links to militants who have the competence to plot and execute suicide bombings.
Ismail Abedi, 23, the bomber's older brother was arrested near a Morrisons in Chorlton on Tuesday.
Amber Rudd told Sky News that U.S. officials provided information to media that Britain preferred to keep confidential for reasons of operational security. "A true gentleman. R.I.P John thoughts and prayers with you family and all of the other victims effected by this tragedy".
Police arrested three people in South Manchester on Wednesday, bringing the total number of arrests related to the attack to four.
"We have been carrying out searches at an address in the Withington area and a man has been arrested". Officers also raided a property in the city's Moss Side neighborhood early Thursday and carried out a controlled explosion.
The images, said to be taken at the scene by United Kingdom law enforcement, show the remnants of a blue backpack, shrapnel and a detonator.
Meanwhile, British news outlets adhered to police exhortations and waited to disclose such details until officials were ready to reveal them.
Britain raised its threat level from terrorism to "critical" after an emergency government meeting late Tuesday amid concerns that the 22-year-old Abedi may have accomplices who are planning another attack. ISIS quickly stepped forward to claim responsibility for the bombings, though police said they had not yet verified the claims.
The number of injured take into account the walking wounded who checked into hospitals a few hours after the attack at a concert by USA actress-singer Ariana Grande on Monday night.
The Government announced that a minute's silence will be held at 11am on Thursday in remembrance of those who died or were affected by the attack.
A United States security official cited by NBC News said his family had warned authorities about him in the past, saying he was "dangerous".
Rudd said up to 3,800 soldiers could be deployed on Britain's streets, taking on guard duties to free police to focus on patrols and investigation.
French interior minister Gerard Collomb believed Abedi travelled to Syria from Libya and had "proven" links with Isis.
Chilling images, released by the New York Times today, appear to show the device which was used by the bomber in the Manchester terror attack.
Manchester police would not comment on information-sharing, but said at a news conference that the families of attack victims were distressed by leaks.
"We encourage anyone who may have information about the individual involved to contact the police without any delay so they can assist with their investigation. Hashim told us, "I know everything about my brother, what he was doing there in Manchester".
"One aspect is whether certain US artists will decide they would rather stay there than come to Europe", said Manfred Tari, an industry expert and contributor to music business research service Music & Copyright.