Three Kurdish fighters were arrested in northern Syria on Saturday in possession of $2 million, Turkish daily newspaper Daily Sabah reported.
The fighters belonged to People's Protection Units (YPG) and were said to be gathering intelligence about the security forces deployed in the region.
They were arrested in the town of Al-Rai in an operation by gendarmerie forces from Turkey's Kilis province.
The report added that the $2 million found in their possession was meant to be delivered to the group's Manbij branch.
According to Turkish-based think-tank SETA, the group has an annual income of up to $1.5 billion generated from drug trafficking in Europe.
Turkey has designated the YPG a terrorist organisation, claiming it to be an offshoot of the Kurdistan Workers' Party (PKK) which is banned in the country and is listed as a terror group by the US and EU.
In January, the US Justice Department announced that the YPG is a "sub-affiliate of" the PKK terrorist group.
"YPG is a sub-affiliate of the Kurdistan's Working Party (PKK), which is designated by the United States government as a Foreign Terrorist Organization," the department said.
According to Turkey, the PKK terrorist group has been responsible for the deaths of some 40,000 people, including women, children, and infants.