Salih Muslim, a prominent former leader of the Kurdish Democratic Union Party (PYD) in Syria, has been arrested in the Czech capital, according to Turkish security officials and the PYD.
Party officials in northern Syria confirmed his arrest to Al Jazeera over the phone, adding that it was not clear if he would be handed over to Turkey.
Muslim was arrested in Prague on Saturday, Turkish officials told state-run Anadolu news agency on condition of anonymity.
Turkey considers the Kurdish Democratic Union Party (PYD) in Syria and its armed wing, the Kurdish People's Protection Units (YPG), to be "terrorist groups" with ties to the banned Kurdistan Workers' Party (PKK).
The PKK has waged a decades-long armed fight against the Turkish state that has killed tens of thousands of people.
The arrest came after Turkey called on the Czech Republic to arrest the former co-leader and sent warrants for his arrest to Prague, Turkish officials said.
The Turkish interior ministry had offered a bounty of nearly $1m on Muslim, who is listed as one of the "most wanted terrorists" in Turkey.
Muslim will be produced before a court, the officials said, adding Czech authorities would decide whether or not he would be remanded in custody.
Czech authorities also asked Turkey to submit the necessary documents for Muslim's extradition, Anadolu reported.
Turkish security officials and the justice ministry have begun the administrative process for the extradition of Muslim.
Turkey - together with the Free Syrian Army (FSA) rebel group - last month launched an air and ground offensive into Afrin in the northwest of Syria to vanquish the US-backed YPG fighters near its border.
