Twenty one Egyptians imprisoned for protesting the government’s surrender to Saudi Arabia of two Red Sea islands have gone on hunger strike over their “unfair” trial.

Heba Mohamed, the wife of Egyptian detainee Nagi Kamel, said on Sunday that ten detainees have been refusing to eat food since last week, and that another 11 joined the protest action on Saturday.

Misr Abdel-Wahed, a sister of one of the prisoners, said three of the hunger strikers were taken to hospital on Saturday as their health conditions deteriorated.

“They took extreme measures by going on hunger strike without the availability of proper health care,” lawyer Mokhtar Mounir said, adding that this was the only way they could express their opposition to the trials.

The Egyptian government has been under fire since it announced in a statement on April 9 that the islands of Tiran and Sanafir fell within the territorial waters of Saudi Arabia based on a maritime border agreement signed with Riyadh the previous day.

On April 15, thousands of people took part in mass demonstrations against the deal. Egyptian riot police forces arrested many protesters.

On May 14, an Egyptian court sentenced 152 protesters to time in prison for participation in a protest rally in central Cairo on April 25. Judicial sources said the court handed down five-year prison terms to 101 of those sentenced, while 51 others received two-year sentences.

All of the 152 individuals were convicted on a single day, in three mass hearings, for breaking a law that effectively bans demonstrations.

The leader of the opposition Egyptian Popular Current, Hamdeen Sabahi, has filed a 10-page complaint at a Cairo administrative court over the contentious deal with Saudi Arabia.

The senior opposition politician said he possesses documents that prove the islands, Tiran and Sanafir, are Egyptian territory and cannot be transferred to Saudi Arabia.

Legal experts and other opposition figures, including exiled politician Ayman Nour, and the country’s Muslim Brotherhood movement have also rejected the legitimacy of the agreement, arguing that relinquishing authority over Egyptian territory is unconstitutional.

Tiran Island is located at the entrance of the Straits of Tiran, which separate the Red Sea from the Gulf of Aqaba. It is an important sea passage to the major ports of Aqaba in Jordan and Eilat in Israel.

Israel briefly took over the island during the Suez Crisis in late 1956, and once more between 1967 and 1982 following the Six Day War.

Sanafir Island is to the east of Tiran Island, and measures 33 square kilometers (13 square miles) in area.

The ownership of the two islands had been handed over to Egypt in 1982, when Tel Aviv and Cairo signed the Camp David accords.