At least 12 pro-Iranian fighters were killed by raids by unidentified aircraft on one of their locations in eastern Syria.
The Syrian Observatory for Human Rights said on Sunday that "eight raids targeted the headquarters of pro-Iranian forces in the eastern countryside of Deir Al-Zour on Sunday before midnight, killing 12 Iraqi and Afghan fighters, and destroying machinery and ammunition."
The observatory was unable to identify the aircraft that launched the strikes, but its director Rami Abdel Rahman suggested that Israel was responsible for carrying out the strikes.
According to the observatory, the raids came at night after Afghan fighters brought in reinforcements from a village near the Iraqi border to the center of a huge gathering of Iranian forces near al-Mayadeen.
Israel rarely confirms that it has carried out raids in Syria, but it reiterates that it continues to confront what it describes as Iran's attempts to consolidate its military presence in Syria and to send advanced weapons to the Lebanese Hezbollah.
It has been repeated in recent times targeting military sites belonging to the Iranian forces and groups loyal to them, especially in the Deir Ezzor region.
Iranian and other Iraqi forces and pro-Damascus groups are deployed in a wide area in the eastern countryside of Deir Ezzor, especially between the border cities of Albukamal and Al-Mayadeen.
Similar strikes on May 31 killed five non-Syrian pro-Iranian fighters in the Badamal district, the observatory said.
On May 17, air strikes killed seven pro-Iranian fighters, according to the observatory, days after they brought in military reinforcements.