Egyptian political groups and families of detained protesters announced they will hold a protest in Cairo on Thursday afternoon calling for the release of detainees.

"We know they are all being denied their basic rights and that their trials are politicised, we want to stand together and declare our solidarity for all those unjustly jailed," the Freedom for the Brave campaign wrote on its Facebook page.

Since a protest law was passed by Egypt's interim government last November, scores of protesters have been apprehended by police in peaceful as well as violent protests.

Prominent activists who took part in anti-Morsi protests were also rounded up when they demonstrated against the strict protest law. Among them are Ahmed Douma and Ahmed Maher, leader of the April 6 Youth Movement, whose trial appeal will be held this week.

Douma, Maher and Mohamed Adel were sentenced to three years in jail and fined LE50,000 in December. Their families, as well as that of prominent activist Alaa Abdel-Fattah -- who is also facing trial but was released from detention on bail in March -- will attend the protest scheduled to be held at Cairo's Opera House in Zamalek.

The demonstration will be held during a week witnessing multiple trials of "revolutionaries and students," the campaign said, calling on all detainees' families to join their demand for the release of those "unfairly imprisoned," including detained Al-Azhar University students and protesters arrested on the anniversary of the 2011 revolution last January.

The demonstration is also sponsored by 6 April Youth Movement, 6 April - Democratic Front and the Revolutionary Socialists.

Since the ouster of Islamist president Mohamed Morsi by Egypt's army after mass protests against him, security forces have conducted a sweeping crackdown on Islamists as well as some non-Islamist activists.

The government insists there are no political prisoners in Egyptian jails, saying all those in detention are facing criminal charges.