Egypt's High State Security Prosecution ordered on Friday the 15-day detention pending investigation of Mohamed El-Qassas, a prominent activist and deputy head of the Strong Egypt opposition party, on charges of spreading false news against the state.

The prosecution is accusing El-Qassas of joining an illegal group that aims to obstruct the law and the constitution and prevent state institutions and public authorities from performing their duties.

El-Qassas and others are also accused of spreading false news about the economic and political situation in the country with the aim of disrupting public order, and serving the interests of the banned Muslim Brotherhood group to shake confidence in the Egyptian state and its institutions.

El-Qassas’ lawyer Mokhtar Mounir told Ahram Online that El-Qassas faces charges along with 50 other defendants – including journalists and members of former presidential hopeful Sami Anan’s campaign, as well as well-known Twitter user Islam El-Refai – who were arrested on charges of contributing to the pro-Muslim Brotherhood TV channel Mekameleen, which broadcasts from outside of Egypt.

El-Qassas’ family said on Thursday that his whereabouts are unknown.

According to Mounir, a security order has been issued to seize El-Qassas' house, from which his family is barred from entering.

In January 2017, El-Qassas was placed by a court on Egypt's terror list, which has around 2,000 names including former president Mohamed Morsi; the Brotherhood’s spiritual leader Mohamed Badie; businessman and owner of Juhayna dairy company Safwan Thabet; chairman of the Wasat Party Abul-Ela Mady; and prominent football player Mohamed Abou Treika.

El-Qassas who announced his resignation from the Brotherhood during the 2011 revolution, has been a prominent activist and member of the political bureau of the Strong Egypt Party, which was founded in July 2012 by its current head and former presidential candidate Abdel-Moneim Abul-Fotouh.

In December 2013, the Egyptian government designated the Muslim Brotherhood a terrorist organisation.