The Committee to Protect Journalists on Friday urged Turkey to release a Syrian reporter who the group said had been detained earlier this week while applying for a residency permit.
The media rights group said Rami Jarrah had been detained in the southern city of Gaziantep, and that he had been questioned about his reporting but the reasons for his detention were unclear.
"Jarrah is known for his independent reporting on the war in Syria, which he has been covering for years at great risk," said CPJ's Europe and Central Asia program coordinator Nina Ognianova.
"Syrian journalists like Jarrah, who have turned to Turkey for safe refuge, should be protected rather than subjected to detention and harassment."
The group said Jarrah was initially held in a detention facility for foreign citizens, but was moved to a different facility on Thursday, and that it was unclear where he was currently being held.
"We call on Turkish authorities to immediately release Rami Jarrah and allow him to work in Turkey without fear of obstruction," Ognianova said.
Turkish authorities had no comment on the reported detention.
Ankara is a key backer of Syria's opposition and says it is hosting more than 2.6 million Syrian refugees.