CAIRO, Sept 3 (Aswat Masriya) - The Giza criminal court upheld on Saturday a decision to renew the detention of political activist Haitham Mohamadeen for 15 days.

The court rejected Mohamadeen's appeal against the decision. 

Mohamdeen, who is a leading figure of the Revolutionary Socialists movement, is accused of belonging to a "terrorist group" which the prosecution did not name, inciting protests and possession of leaflets at his house.

He was arrested last April amid a security campaign ahead of protests planned on Apr. 25  against the Egyptian-Saudi maritime border demarcation agreement.

Egypt and Saudi Arabia signed an agreement earlier in April stipulating that the Red Sea islands of Tiran and Sanafir fall within Saudi Arabia's territorial waters.

The agreement had stirred controversy, with critics accusing President Abdel Fattah al-Sisi of "selling Egypt" to Saudi Arabia in return for aid.

In June, Egypt's administrative court annulled the agreement and affirmed that the two islands fall within Egypt's borders.

The Egyptian government however maintains that both islands belong to Saudi Arabia and challenged the annulment of the agreement before the Supreme Administrative Court and  the Supreme Constitutional Court.

The Tiran Island is located in the Gulf of al-Aqaba, about 5 or 6 km from the Sinai Peninsula, and it has a total area of about 80 square km. Sanafir Island lies to the east of Tiran with a total area of 33 square km.

Located at the mouth of the Gulf of Aqaba, the two islands are strategically significant as they both control maritime activity in the gulf.