Turkey's decision Thursday to free two VICE News correspondents jailed on charges of aiding terrorism was greeted by cautious optimism from press freedom advocates and journalists around the world. But as their colleague, Iraqi journalist Mohammed Ismael Rasool, languished in detention, one press freedom advocate worried the arrests were intended to send a hostile message to the country's foreign correspondents.

Jake Hanrahan and Philip Pendlebury, two British journalists reporting for VICE News, were arrested along with Rasool last week and charged with "knowingly and willingly" aiding a terrorist organization. After nearly a week in detention, Pendlebury and Hanrahan were freed earlier this week and are scheduled to be deported from the country. As of this morning, Rasool remained locked up.

All three were reporting on escalating tensions between authorities and the youth wing of the Kurdistan Workers' Party, also known as the PKK.

Robert Mahoney, deputy director for the Committee to Protect Journalists, reiterated CPJ's call for Turkey to release Rasool and warned that the VICE arrests could be "a shot across the bow" for future journalists looking to report on conflicts in southeast Turkey.

"It is clearly a worrying signal that people who are journalists who are entering the southeast to do reporting on the PKK are once again in the sights of Turkish security services," Mahoney said.

The arrests are a forbidding symbol for foreign correspondents in Turkey, including some who moved to Istanbul from Cairo amid the instability that followed the Arab Spring, Mahoney said. Although the administration of Turkish President Recep Tayyip Erdogan has seen a crackdown on Turkish journalists perceived as unsympathetic to his regime, the government generally leaves foreign correspondents alone.

Turkish authorities are known for ratcheting up scrutiny for any journalist, foreign or domestic, that travels to the predominantly Kurdish southeast to report on clashes between the Kurdistan Workers' Party and government forces. But in most of those cases, Mahoney said, they are quickly let go. In January, Dutch freelance journalist Frederike Geerdink was arrested at her home while reporting from the southeastern city of Diyarbakir and charged with spreading "terrorist propaganda." She was acquitted by a court, but a Turkish prosecutor challenged the decision.

It's unclear how long Rasool will remained locked up, although there was an encouraging sign Thursday. Rasool's lawyer, Ahmet Ay, told The Guardian that he expected to be freed "soon." However, pretrial detention in Turkey can stretch for years, as it has in the case of online reporter Cüneyt Hacıoğlu, who was arrested in September 2013 and had not been charged as of 2014. The tendency of authorities to keep correspondents in legal limbo earned Turkey the distinction of being the worst jailer of journalists two years running in 2012 and 2013.