"We can confirm the detention of two people,” a spokesman for the National Republican Guard (GNR) said, declining to provide further information on the case, on the grounds that it is being overseen by Lisbon prosecutors.

In total, 37 defendants are now being held on remand, of which 23 were detained on the day of the incident, and the rest in June and July. Among them is former Fernando Mendes, former leader of the Sporting fan club, Juventude Leonina.

On 15 May this year, members of the Sporting squad were attacked at the club’s academy in Alcochete, south of Lisbon, by a group of around 40 hooded self-described fans, who assaulted some players, coaches and other staff.

The 37 defendants currently being held are suspected of several crimes, including terrorism, grievous assault, aggravated threat, abduction and harm with violence.

Following the attack on the academy, nine footballers rescinded their contracts with Sporting.

Earlier this month, the Lisbon appeal court upheld the detention on remand of eight of the suspects, according to prosecutors. The court has yet to comment on outstanding appeals being made by most of the detainees in the case.