The BBC has published an interview with a Syrian, who revealed that he had been recruited by one of the commanders of the pro-Turkish Syrian National Army and was now in Azerbaijan.
The man said he had been offered to protect military facilities for $2,000 a month, and was not expected to participate in hostilities.
They entered Azerbaijan through the territory of Turkey.
The Syrian said that despite assurances, he and other mercenaries were involved in battles with Armenian forces in Karabakh. He says he saw the bodies of 10 Syrians who died, and 70 Syrians were injured and did not receive medical attention.
The BBC reports from the north of Syria that several families received news about the deaths of their relatives in Azerbaijan.
Azerbaijan and Turkey have strongly denied recruiting mercenaries and sending them to Karabakh.