Revolutionary Socialist and labour lawyer Haitham Mohamedein was released without bail late on Saturday after facing questioning by Suez prosecutors, according to lawyer Ramy Ghanem.

The prosecutors grilled Mohamedien on accusations of "belonging to a secret organisation" – that is, the Revolutionary Socialists – "obstructing the authority of the state," and "undermining social institutions," Ghanem added.

Evidence brought against Mohamedien included a sketch from his personal journal outlining routes for the 30 June protests that led to former president Mohamed Morsi's overthrow. Mohamedien, who played a role in planning the 30 June marches, confirmed that the handwriting was indeed his own.

In a statement on his Facebook, Mohamedien thanked "all revolutionaries" – and especially those working for the release of detainees – for their solidarity, adding that he was "confident we will not be bullied by repression."

Mohamedein was arrested at a military checkpoint close to Suez on Thursday en route to meet with labour clients, and he was ordered detained for an extra four days on Friday. The reason for his arrest remains unclear.

Demonstrators gathered Saturday outside the prosecutor general's office in downtown Cairo to demand Mohamedein's release.

The protest, which was called for by the Revolutionary Socialists, was also joined by members of the April 6 Youth Movement and the Egyptian Current Party, in addition to several revolutionary figures such as activist Alaa Abdel-Fatah and TV anchor Reem Magued.

Another protest in solidarity with Mohamedein was held in Egypt's second largest city of Alexandria, outside Al-Bahareyia Court on Mansheya Square.