Egyptian rights activists are posting photos on social media showing themselves behind symbolic bars to demands an end to what they say is the expanding and illegal use of solitary confinement for political detainees.

The photos are part of a month-long campaign launched on June 12, calling on relatives of detainees subjected to solitary confinement to file complaints over the issue to parliament and the chief prosecutor against the country's Prisons Authority.

The campaign was inspired mainly by the case of Malek Adly, a prominent rights lawyer who has spent most of the six weeks since his detention in May in solitary confinement, according to his wife and lawyers.

Authorities have detained thousands of government critics since 2013 in what is seen as Egypt's biggest crackdown in decades.