Hisham Kassem’s al-Tayyar al-Hurr plans to back an opposition candidate to President el-Sisi in the next election.

Kassem is a leader of al-Tayar al-Hurr, or Free Current, a liberal group formed in June in opposition to the government of President Abdel Fattah el-Sisi, who is expected to run for a third term by early 2024.

Fellow al-Tayar al-Hurr organiser Gameela Ismail said the coalition intends to offer or support a candidate for the election, and that the government had been pressuring members since its formation.

Rights groups estimate tens of thousands of people have been jailed for political dissent under el-Sisi, who took power after leading the 2013 coup that overthrew the country’s first democratically elected president, Mohamed Morsi.

Kassem was detained on Sunday, soon after the release of several high-profile activists, including Ahmed Douma, last week and researcher Patrick Zaki and rights lawyer Mohamed el-Baqer in July.

The US Department of State welcomed the releases, but urged Egypt to release “all unjustly detained political prisoners”.

Lawyer Nasser Amin told the Reuters news agency on Wednesday that the case’s quick referral to trial before a ruling on a request for bail was unusually harsh for the crime. His trial is set for September 2.

“Hisham Kassem committed the crimes of insult, slander, and assault,” said a security source at the Ministry of Interior.

“Legal measures were taken against him, like in any case, and he was presented to the relevant prosecution for investigation in the presence of his lawyer.”

Kassem in recent months has been especially critical of el-Sisi, an ex-general, and his government, which over the last year and a half has been mired in an economic crisis.

“The change that needs to happen is not just about Sisi no longer being in power, but a restructuring of the Egyptian economy that cannot happen with the military in power,” he said in a BBC interview in July.

The government has sought to address freedom and human rights issues in recent years, including opening a national dialogue with civil society leaders and granting amnesty for some prominent prisoners.

Critics have dismissed the measures as cosmetic and said arrests have continued.

The initial slander case against Kassem was brought on Sunday by Kamal Abu Eita, a former government minister and member of a committee tasked with recommending pardons.

Kassem initially refused cash bail, indicating in Twitter and Facebook posts on Sunday that he felt the case was political.

“I am more honourable than Abdel Fattah el-Sisi and all his men and his regime,” he said.