Egyptian authorities have arrested the head of an activist group that played a key role the country’s 2011 revolution against former dictator Hosni Mubarak.

Amr Ali, the April 6 Youth Movement’s coordinator, was arrested in the capital, Cairo, on Tuesday, the DPA reported.

The group said he was being held at a state security building, and state-run Al-Ahram newspaper quoted a local detective chief as saying that the arrestee was undergoing interrogation.

The movement earned renown for its young activists’ defiant spirit and influential role during the revolution against Mubarak.

The revolution was followed by the rise to power, through democratic elections, of President Mohammed Morsi in 2013. Morsi was, however, deposed that same year by then army chief Abdel-Fattah al-Sisi, who has overtaken the country’s presidency.

Many of Egypt’s most prominent democracy activists have been jailed since Morsi’s overthrow. Those include Ali’s predecessor, Ahmed Maher, who is currently serving a three-year jail term for taking part in protests against the government of Sisi.

In 2014, the revolutionary group announced the start of a campaign titled “Against you” in protest at the candidacy of the former military leader in presidential elections, where he was set to compete against sole contender and leftist politician Hamdeen Sabahi. In launching the campaign, the movement described Sisi as a disciple of Mubarak.

A court ruling has banned the group, arguing that it tarnishes Egypt’s image abroad.