CAIRO (Reuters) - Egyptian authorities have released high-profile Irish detainee Ibrahim Halawa following his acquittal last month of charges including murder, in a four-year mass trial criticized by human rights groups.

Halawa, a student, and three of his sisters were charged along with nearly 500 others with a host of crimes including breaking into a mosque, killing 44 people, and illegal possession of firearms in violence that followed the military’s overthrow of Egypt’s Islamist president, Mohamed Mursi, in 2013.

Irish Foreign Minister Simon Coveney told Irish national broadcaster RTE on Friday that Halawa was likely to be able to fly home by Monday following his release late on Thursday.

“This is a great moment for Ibrahim and his family – a moment for celebration, and a moment for savoring freedom, and I want to wish Ibrahim Halawa and his family all health and happiness for the future,” Coveney said in a separate statement.

Egyptian rights activists say they have faced the worst crackdown in their history under President Abdel Fattah al-Sisi, who was elected president in 2014, a year after as armed forces commander he led the military’s toppling of Mursi.

Halawa was 17 when he was arrested in 2013 with hundreds of others as part of the crackdown on protests. Since then he had been held in pre-trial detention, where he said he was regularly tortured.

The defendants in the case had all faced the death penalty but none received it, though hundreds were given sometimes hefty jail sentences.

Rights groups welcomed Halawa’s release.

“After four years of unjust detention, today Ibrahim Halawa finally walks free. He should never have been jailed in the first place and it is utterly outrageous that he was forced to spend a single minute of his young life behind bars.” said Najia Bounaim, North Africa Campaigns Director at Amnesty International.

Reuters was not immediately able to reach Halawa’s family for comment on Friday, but his sister Fatima told RTE in a radio interview: “It’s beyond description ... It’s amazing to finally know that Ibrahim is out and he’s released and he’s safe.”