“We have evidence that he is involved in Daesh (Islamic State) with his brother. We have been following him for more than one month and a half,” a spokesman for a local counter-terrorism force told Reuters.
“He was in contact with his brother and he knew about the attack.”
The Tripoli-based anti-terrorism Special Deterrent Force said Hashem, 20, confessed that both he and Salman were a part of IS.
Salman’s father, Ramadan Abedi, was also detained by Libyan authorities on Wednesday.
“The reason we have gone to critical is because he is still out there and the fear is that he will strike again before they get caught.”
British Prime Minister Theresa May has raised the country’s terror threat level from “severe” to “critical”, meaning authorities expect another attack is imminent.
Greater Manchester Police have declined to comment on the search for the bombmaker officially, but confirmed that Mr Abedi did not act alone in carrying out his deadly attack on concertgoers after the US pop stars performance in the city in England’s northeast.
Chief Constable Ian Hopkins said the level of police activity in the investigation was “intense and is continuing at a fast pace”.
“I think it’s very clear that this is a network that we are investigating and, as I said, it continued at a pace, there’s extensive investigations going on and activity taking place across Greater Manchester as we speak,” he told reporters on Wednesday afternoon.
SUICIDE BOMBER’S SUSPICIOUS TRIP
The Manchester bomber returned from a mysterious trip just days before he detonated the bomb inside Manchester Arena.
It has been revealed that Salman Abedi took a three-week trip to Libya, where his parents hail from, and then carried out the terrorist attack just days after he returned to Manchester.
Police and intelligence officers are now investigating why the suicide bomber took the trip and who he met there.
There are also reports in the British media that Mr Abedi recently visited Syria, a hot bed for Islamic State.
The new details come after police confirmed that Mr Abedi, 22, was not a lone-wolf terrorist but was, in fact, part of a “network”.
Mr Abedi died in Monday night’s attack, but police have since arrested six people in connection with the atrocity. Among them is Mr Abedi’s brother, Ismail, 23.
A woman was arrested late Wednesday after an armed raid on a block of flats in the Manchester suburb of Blackley.