The Manchester Arena bomber’s older brother has fled the UK after being called to give evidence to the public inquiry into the attack.
One of Salman Abedi’s childhood friends was also arrested while trying to leave the country on Monday.
Ismail Abedi had been given a court order requiring his attendance at the public inquiry on Thursday, after he and his parents previously refused to give evidence.
Ahmed Taghdi, a friend of Salman’s, had been told to appear on the same day and was due to be questioned for three hours according to an official timetable.
It was hoped that both witnesses would give evidence on how Abedi was radicalised in the lead-up to the bombing, which killed 22 victims on 22 May 2017.
Paul Greaney QC, counsel to the public inquiry, said on Tuesday that Ismail Abedi had refused to cooperate and so had been ordered to attend on Thursday.
“However, we understand that he is not currently in the country and there is no indication as to when he will return,” he added.
“Ismail Abedi clearly has important evidence to give to the inquiry and we urge him today to give evidence to the inquiry legal team either directly or through his own legal representatives.
“As he surely must understand, if he does not do so the public may infer he has something to hide.”
Mr Taghdi was also ordered to give evidence, and was told on Friday that if he did not attend the inquiry this week he would be arrested.
Mr Greaney said that he attempted to leave the country on Monday and, as a result, was arrested.
The hearing was told that he was able to provide evidence of a return ticket to the UK on 20 October, before his attendance at the inquiry the following day.
Both Ismail Abedi and Mr Taghdi were arrested after the bombing and questioned by police, but were not charged with any offences and deny any involvement in or knowledge of the plot.
They have been told that they have the right not to answer any questions that may incriminate them at the public inquiry, sitting in Manchester.
There have been a series of protracted legal battles by inquiry lawyers to obtain evidence from Salman’s family and associates.
The bomber’s mother and father are among people the public inquiry has said it wanted to question but they are also believed to have left the UK.
Mr Greaney told the hearing: “The inquiry legal team has done all it can to obtain evidence from Salman Abedi’s immediate family. Ramadan Abedi, his father, Samia Tabbal, his mother and their younger children are all presently in Libya as far as the inquiry is aware.
“Although Ramadan and Samia have been contacted, they have refused to provide any statements or evidence of any kind.”
Salman detonated the bomb alone, at the end of an Ariana Grande concert, but his younger brother Hashem Abedi was later found to have been deeply involved in the plot and preparations.
He was handed a life sentence for murder last year, after prosecutors said he was “just as responsible” for the deaths of the victims as his suicide bomber brother.
Last week, a lawyer representing a terror convict who allegedly “groomed” the terrorist said he would refuse to ask questions if he is ordered to give evidence at the public inquiry.
Abdalraouf Abdallah, 28, has not answered questions from the inquiry’s legal team from prison, where he is serving a sentence for helping Isis fighters travel to Syria.
The inquiry previously heard that Mr Taghdi, 29, accompanied Salman to visit Abdallah in jail.
He also helped Salman and Hashem buy a car that was used to store bomb components ahead of the terror attack.
Sir John Saunders, the chair of the inquiry, refused to drop an order compelling Abdallah to attend on Wednesday.
He said the inquiry’s remit meant it must investigate Salman’s radicalisation, his relationship with associates including family members and friends, and whether he or relatives should have been referred to the Prevent counter-extremism scheme.
Speaking to Tuesday’s hearing, Mr Greaney said: “It is very hard indeed for anyone with a shred of decency to comprehend why a person could ever think of detonating a suicide bomb in the midst of a crowd, killing or maiming many innocent victims.
“However, if we are to do everything in our power as a society to prevent such things happening in future we must do what we can to understand what motivated Salman Abedi to commit such a horrific act.”