A prominent Egyptian rights lawyer, who had raised a legal suit against the Egyptian president's decision to hand two Red Sea islands to Saudi Arabia, has been arrested and ordered to be held in custody for 15 days, pending an investigation into a list of allegations, including attempts to overthrow the government.

Malek Adly's detention on Friday is part of a wave of arrests in Egypt as security forces put down protests against President Abdel-Fattah el-Sisi's decision on the islands.

Adly, a member of the April 6 youth movement that was part of the uprising that ousted President Hosni Mubarak from power in 2011, has appeared on TV talk shows, speaking out against the islands' handover.

He was also among a group of lawyers who filed a lawsuit over the case of the islands.

Two others from the group were also arrested. They were arrested in a police raid of the Journalists' Syndicate on Sunday, which sparked protests by hundreds of journalists who called for Interior Minister Magdy Abdel-Ghaffar's dismissal and a presidential apology.

Both Sisi and Abdel-Ghaffar have ignored the demands.

READ MORE: Egypt journalists demand dismissal of interior minister

The interior minister on Thursday attended the inauguration of a mega project for land reclamation hailed by Sisi as one of his "unprecedented" achievements. In his half-an-hour speech at the event, Sisi repeated several times, "I am not afraid" - a statement observers believe was meant for his critics.

Crackdown on dissidents

Sisi, Egypt's army chief-turned-president, has orchestrated one of largest ever crackdowns on dissidents in the country, following the military's deposing of President Mohamed Morsi in July 2013.

An anti-protest law issued months later led to mass arrests of thousands of protesters, mostly Morsi's supporters or pro-democracy advocates. The law and heavy-handed security measures have stifled street demonstrations.

However, on April 15, nearly 2,000 protesters rallied to denounce the handover of the Tiran and Sanafir islands. The deal took many Egyptians by surprise, especially since it came during Saudi king's visit to Egypt, during which several multibillion dollar deals were struck.

Sisi and the government have defended the decision by saying the islands at the mouth of the Gulf of Aqaba were Saudi territory and that the kingdom asked Cairo in 1950 to protect them from Israel.

Source: Agencies