CAIRO: A former Egyptian presidential candidate and a prominent rights lawyer who challenged the government for handing over islands to Saudi Arabia was detained Tuesday on suspicion of illegal political work, a judicial official said.

Khaled Ali was summoned by the prosecution for questioning on suspicion of having set up an unregistered political party, the official said.

But according to his lawyer, Malek Adly, Ali is being sued by a private citizen over a photograph in which he appears to make a rude hand gesture on the steps of a Cairo courthouse. Ali denies the authenticity of the photo.

The prosecution ordered his detention for 24 hours.

His legal troubles come as opposition groups complain of a crackdown ahead of the 2018 presidential election which incumbent Abdel-Fattah al-Sisi is expected to dominate.

Ali was the main lawyer to bring a case against the government after it agreed to hand over two islands in the Red Sea to Saudi Arabia in April last year. The agreement to transfer the islands of Tiran and Sanafir sparked rare protests in Egypt, which bans all but court approved demonstrations.

Ali, who ran in the 2012 election that brought to power Islamist President Mohammad Morsi, has suggested he might run against Sisi in the next presidential election.

Dissidents accuse Sisi of having installed a repressive regime since the then-army chief ousted the unpopular Morsi in 2013.

But Sisi also enjoys widespread support among Egyptians, who say the country needs a firm hand to cope with years of tumult and a deadly militant insurgency.