A British man has been arrested as part of an anti-terror operation while on holiday in Turkey, the BBC has learned.
Ex-soldier Joe Robinson, from Leeds, is understood to be accused of sharing material on social media from his time in Syria with Kurdish militia the YPG.
Mr Robinson, 24, his Bulgarian fiancé Mira Rojkan, and her mother Veselina, were detained in a police raid at the resort of Didim, western Turkey.
The Foreign Office said it has requested consular access.
The group's mobile phones, computer and other digital devices were seized by police.
Ms Rojkan and her mother have now been released but friends told the BBC Mr Robinson remains under arrest and will appear in court on Monday.
'Want my son home'
Mr Robinson, who is originally from Lancashire, spent five months fighting as a volunteer with the YPG against the so-called Islamic State group and has previously spoken about his experiences in media reports.
Although the YPG is not a proscribed group in the UK, Turkey views it as the extension of the outlawed Kurdistan Workers Party (PKK).
According to reports in Turkish media, the police operation was carried out against the PKK.
Mr Robinson's mother Sharon Chimejczuk told the BBC: "I just want my son home safe".
"He has done nothing but help innocent civilians. His whole family are concerned for his wellbeing and urge the British authorities to help bring him home."
Ms Rojkan, who lives with Mr Robinson in Leeds, said she was extremely distressed by her experience. She said she had been allowed to speak with her fiancé since his arrest and he is very worried.
Speaking to the BBC, Ms Rojkan said "I just want the love of my life back. He's wanted to do nothing but help people. He doesn't deserve this."
A Foreign Office spokeswoman said: "We are aware of the detention of a British national in Turkey and have requested consular access."
Mark Campbell from the Kurdistan Solidarity Campaign said: "Unfortunately, Joe has gone on holiday to Turkey not realising the kind of state it has now become.
"Turkey continues to criminalise the Kurdish question and has jailed tens of thousands of Kurdish people, including elected MPs and mayors, simply for peacefully campaigning for Kurdish rights."