Relatives of those killed in the Manchester Arena bombing have been “very anxious” about attending the inquests after receiving threats, a court has heard.

They were reassured that security at the inquests was being taken very seriously “at the highest level”.

Police were stationed outside Manchester town hall on Thursday for a pre-inquest hearing into the deaths of the 22 people killed in the attack on an Ariana Grande concert on 22 May last year.

The names of the dead were read out and a minute’s silence was held at the start of the proceedings. Many family members were present.

The inquests will not begin for at least a year while the Crown Prosecution Service waits for Libya to extradite Hashem Abedi, the younger brother of the bomber, Salman Abedi. If he is returned to the UK he will face trial for 22 counts of murder, one of attempted murder and another of conspiracy to cause an explosion.

The bomber’s inquest will be held separately from those of his 22 victims. “There are multiple compelling reasons why Salman Abedi’s inquest should not take place at the same time. To do otherwise would inevitably add to the distress of the families,” said Paul Greaney QC, counsel to the inquest.

Most of the families have engaged lawyers to represent them in the process, apart from the husband of Alison Howe, from Oldham, who died alongside her friend Lisa Lees. Stephen Howe asked the coroner, Sir John Saunders, for more information to be released about the 23 people who have so far been arrested and bailed in connection with the attack, but he was told that to do so ran the risk of prejudicing any future criminal trial.

The families were told they would have the opportunity to submit to the inquest “pen portraits” of those killed, and that if they were willing to sign confidentiality agreements they would receive a raft of sensitive information about the circumstances surrounding the attack.

Some were worried about attending the hearing, their lawyer said. “There is reason to believe that on a public forum threats have been made and they are very anxious indeed,” said John Cooper QC, who is representing the families of John Atkinson, Kelly Brewster, Wendy Fawell, Megan Hurley, Nell Jones, Angelika and Marcin Klis, Eilidh MacLeod, Elaine McIver and Martyn Hett.

Saunders said information about the threats should always be passed straight to police, and Greaney sought to reassure the families they would be safe. “The subject of security is under consideration at the highest level and is taken very seriously indeed,” the QC said.

In opening remarks at the start of the hearing, Saunders promised a “thorough and detailed examination of the evidence”, ensuring the “full facts are brought to light”. He said the inquests would hear “difficult and upsetting evidence” and counselling services would be available for the families.

The coroner refused a request by Salford University to be considered an interested persons in the inquest, which would have given the university the right to participate actively in proceedings.

Saunders said he would like the institution to share with him information on Salman Abedi’s studies. Abedi was in his second year of a degree in business and management at Salford when he carried out the attack, and the university said it had information about his “academic performance and engagement in general”.