Joe Robinson was detained while holidaying on Turkey's western coast after posting pictures on social media allegedly showing himself in camouflage gear taking part in Kurdish People's Protection Units (YPG) operations in Syria.

Ankara considers the YPG a terrorist group and the Syrian branch of the Kurdistan Workers' Party (PKK), which has waged an insurgency inside Turkey since 1984.

"He has been released but he must remain in Turkey. The next hearing is scheduled for March 12," Robinson's lawyer, Mehmet Celal Baykara, told AFP.

Robinson's wife, a Bulgarian citizen, was initially detained with him but later released under judicial control. Her mother was also detained but freed without charge.

According to British press reports, Robinson is a former soldier who served in Afghanistan in 2012, and who spent several weeks in Syria in 2015 providing medical assistance to the YPG.

He had been arrested upon his return to Britain on suspicion of terror offences but the charges were dropped after 10 months.