The 22-year-old student arrested on terrorism charges after a major security alert in Rotterdam last month has been released from jail.

However, Jimmy F remains a suspect in connection with the case, officials said.

F claims to have been trying to track down terrorists himself. His lawyer Karianne Bal told the Volkskrant last month: ‘my client’s only goal was to unmask terrorists. He has been doing this for years. I can’t understand why he is being held.’

The alleged terrorist was picked up by an anti-terror unit in the wake of a tip-off from the Spanish Guardia Civil about a possible attack on a concert by the American band Allah-Las in Rotterdam on August 23. The threat was credible enough for mayor Achmed Aboutaleb to cancel the event.

F, who studies safety and security management, had allegedly posted concrete threats about the Rotterdam concert on messaging service Telegram.

But according to the Volkskrant Jimmy F is a member of the international online group Syria General whose aim is to find terrorists and give information about their whereabouts to police and security services. The group is said to have close ties with Russia, and to support Syria’s president Assad.