Amnesty International and Palestinian cultural institutions have launched an appeal for help for 23-year-old Palestinian circus performer and teacher Mohammad Abu Sakha, held by Israel for nearly three months without trial.
Abu Sakha was arrested on December 14 in the occupied West Bank, and held since January in administrative detention, the controversial measure under which Israel can hold suspects without trial for periods of six months, renewable indefinitely.
Amnesty said Israel believes Abu Sakha is a member of the leftist Popular Front for the Liberation of Palestine (PFLP), which is considered a militant movement by Israel due to its armed wing.
The Israeli army could not immediately comment on the reasons behind Abu Sakha's detention.
The Palestinian Performing Arts Network (PPAN), representing artists and cultural institutions, said it was "deeply concerned" over the detention of Abu Sakha, who since 2008 has been part of the Palestinian Circus School in Bir Zeit, first as a student and later as a clown and teacher.
PPAN called on artists and cultural organisations "to raise awareness of Israel's illegal policy of administrative detention" and pressure Israel to release Abu Sakha.
Amnesty called to pressure Israel ahead of a military court hearing of Abu Sakha's appeal against his detention, scheduled for March 21.
Abu Sakha's mother was allowed to visit him once in the Megiddo prison in northern Israel, where he was entertaining his fellow inmates to help the time pass, Amnesty said.
Administrative detention is intended to allow authorities to hold suspects while continuing to gather evidence, with the aim of preventing further attacks in the meantime.
The system has been criticised by Palestinians, human rights groups and the international community.
More than 7,000 Palestinians are currently in Israeli jails, of whom approximately 10 percent are under administrative detention, according to Palestinian rights groups.
One Israeli Jew has been held under the measure for seven months on suspicion of being a leader of a group of extremists targeting Palestinians and Christians in hate crimes.