The Russian Defense Ministry confirmed four of its soldiers had been killed but did not say precisely where or when
At least 26 Syrian government forces and nine Russian fighters were killed in an Islamic State (IS) group attack earlier this week in Syria's eastern desert, a monitor said Sunday.
The Syrian Observatory for Human Rights said the militants had targeted a group of Syrian and allied Russian fighters near the town of Mayadeen in Deir Ezzor province on Wednesday.
"There were 35 pro-government forces killed, including at least nine Russians. Some of those Russian nationals were government troops, but not all of them," said Observatory head Rami Abdel Rahman.
The remaining 26 were all Syrian forces, he told the AFP news agency.
Earlier on Sunday, the Russian Ministry of Defence said four soldiers were killed by rebel shelling in Deir Ezzor province after several rebel groups attacked a Syrian army artillery battery.
Two Russian military advisers who directed the fire of the Syrian battery were killed while two more died of their wounds after being taken to a Russian military hospital. Three more were wounded in the attack, the Ministry said.
"Several groups of terrorists attacked an artillery battery of the Syrian government forces at night in the Syrian province of Deir ez-Zor. Two Russian military advisers, who directed the fire of the Syrian artillery, were killed on the spot," the ministry said according to the Russian news site Sputnik.
It did not give a date or precise location, but the Observatory said it was the same incident as the IS attack near Mayadeen.
Forty-three of the attacking militants were killed and six vehicles were destroyed, the ministry said.
— Dylan Collins (@collinsdyl) May 27, 2018
Russia has been a staunch backer of Syrian President Bashar al-Assad. Russian ground and air forces have been crucial in helping Assad recapture most territory lost in the early stages of the nation's seven-year-long civil war.
A local Russian newspaper in the Siberian city of Chita also reported on the funerals of four soldiers it said were killed in Syria on 23 May.
The Russian statement raised the official count of soldiers killed in Syria to 92.
The biggest number of casualties was in March when a transport plane crashed at Hmeimim airbase, killing all 39 people on board.
As well as Russian soldiers, the presence of Russian mercenaries has been reported in Syria. In February, up to 200 Russian contractors were believed to have been killed by US air strikes after pro-government forces launched an assault on US-backed Kurdish forces in Deir Ezzor province.