The Reporters Without Borders watchdog on Thursday condemned Israel's arrest and continuing detention of a Palestinian journalist working for the Arabic-language Al-Quds newspaper in Jerusalem.
Mohamed Jamal Abu Khdeir was arrested on November 6 on charges of endangering Israeli national security, the watchdog said.
On Wednesday, authorities extended his detention until November 18, and his family and lawyer have not been able to visit him in prison, the group said.
A gag order was also placed on coverage of Khdeir's case in Israeli media on November 10, and will remain in place until November 19.
Police were not immediately able to comment on the case.
"We call for Khdeir's immediate release and the lifting of the gag order on Israeli media coverage of his detention," the watchdog urged.
"Detaining this journalist in connection with his work and the court order banning coverage of the case are a direct violation of freedom of information, democratic principles and the rule of law."
Khdeir was arrested at Ben Gurion airport as he returned from Cairo. He had been covering an Arab League foreign ministers meeting and was accused of "meeting Israel's enemies," Reporters Without Borders said.
He is currently held at the Ashkelon interrogation centre.