Leftist presidential candidate and labour lawyer Khaled Ali
was present at the Saudi Arabian embassy in Giza on Tuesday to protest against the charges levelled on Egyptian lawyer Ahmed El-Gizawi for defaming King Abdullah bin Abdul-Aziz Al-Saud.
El-Gizawi, who was sentenced in absentia, is expected to receive 20 lashes on Friday and a one-year jail sentence after he filed a case against the king over the illegal detention of Egyptians in Saudi prisons.
He was travelling with his family to Jeddah when he was detained on Tuesday, 17 April.
Ali called on the Saudi authorities to officially apologise to El-Gizawi, allow him to complete his Umra pilgrimage and permit him to return to Egypt.
Khaled Ali has made his name promoting social justice and defending the rights of workers, peasants and students over the course of the last two decades.
Ali announced his intention to run for president in March 2012 on a programme of achieving the revolution's goals. His presidential campaign emphasises social equity, the redistribution of wealth, civil liberties and the revolutionary course as a continuing struggle.
Presidential elections will take place on 23 and 24 May, and the president will be named on 21 June after a runoff voting round on 16 and 17 June. A final list of eligible presidential candidates will be announced on Thursday.