However Rami Jarrah said in his post that his detention appeared to be related to his work in Syria.
His arrest caused concern among media groups, who called for his release.
Jarrah - who met Turkish President Recep Tayyip Erdogan in January - was held in the city of Gaziantep.
He was reported to be applying for a residence permit at the time.
"The location I was transferred to late Wednesday evening contained prisoners that were all held under the same suspicion of being terrorist elements, all have not been charged and some have been there for up to nine months after having being declared innocent by a court of law," Mr Jarrah said in his Facebook post.
"It disturbs me that I was placed in this situation given my background and obvious distance from such an accusation."
The reporter said that while he understood "the pressure the Turkish government is under" and the responsibility it has to prevent terrorism, a little more research by the authorities would have prevented unnecessary hardship.
The Committee to Protect Journalists said at the time of his arrest that Syrian journalists should be protected rather than detained.
Jarrah founded the independent citizen journalist group Ana Press, providing reports to international media, after leaving Syria.
He was initially held in a detention facility for foreign citizens, but was moved to a different facility on Thursday, the CPJ said.
Supporters say Jarrah is well known for his independent reporting, often carried out at great personal risk.
Jarrah, who was brought up in the UK, fled Syria with his wife and child in 2011, fearing that he was in danger, but continued to go back to report.
Press freedom 'a major concern'
Turkey urged to free Syrian journalist

Joshua Wong, Nathan Law and Alex Chow are accused of climbing a fence to break into a government compound at the start of the demonstrations.
Mr Wong, 18, has said he did not do anything illegal.
The protests, against proposed changes to Hong Kong electoral system, began in late September.
At the height of the movement, tens of thousands of people were occupying major streets demanding fully free elections for the territory's next leader, after Beijing said it would vet potential candidates.
The three students were among a large group of people who stormed the fenced-off Civic Square inside a government compound on 26 September, as an act of protest.
Images of the students being forcibly removed from the square by police, and other subsequent allegations of abuse of force by police, invigorated the protest movement.
Mr Chow has now been charged with taking part in an illegal assembly and Mr Law with inciting others to take part, while Mr Wong, leader of the Scholarism movement, faces both charges.
Mr Wong could be jailed for up to five years, but said he would not regret his actions and that it was a "political prosecution".
He said the break-in was "the best decision I have made within the four years I have been involved in the social movement and student movement".
Mr Wong's lawyer, Michael Vidler, said charging the trio so long after the event was "totally flawed" and a "clear abuse of process", AFP news agency reports.
Mr Wong and Mr Law are already facing charges of obstructing police officers.
A Syrian journalist who was arrested on Wednesday in Turkey has been released without charge and with no explanation as to why he was detained, he announced on Facebook.
[NEXT_CONCEPT]
Three prominent Hong Kong student leaders have been charged over their roles in the pro-democracy "Umbrella Movement" of 2014.