At least 92 Russian soldiers have been killed in Syria since September 2015, Russia’s defence ministry says.

Four Russian military personnel and dozens of rebel fighters have been killed during a battle in eastern Syria’s Deir Az Zor province, according to Russian officials.

Fighting erupted after several armed groups attacked an artillery battery belonging to Syrian government forces, Russian news agencies reported on Sunday, citing a defence ministry statement.

Two Russian military advisers who directed fire from the Syrian battery were killed on the spot. Five other personnel were wounded and taken to a Russian-run military hospital, where two later died from their wounds.

According to the defence ministry statement, cited by AFP news agency, 92 Russian soldiers have been killed in Syria since Russia entered the country’s ongoing war in September 2015.

Forty-three rebels were also killed during the battle, the ministry said, adding that “several mobile terrorist groups attacked Syrian government artillery at night”. The statement did not make clear when the fighting, which lasted for about one hour, took place.

Moscow helps turn tide in Assad’s favour

Russia is the main military backer of Syrian President Bashar al-Assad in his country’s seven-year civil war that has killed hundreds of thousands of people and displaced millions.

Moscow’s intervention in 2015 tilted the conflict in favour of Assad’s forces, who have in recent months made territorial gains against armed groups, including the Islamic State of Iraq and the Levant (ISIL, also known as ISIS).

Since then, Russia mainly conducted air raids against groups opposed to the government, including the Syrian National Coalition, ISIL, al-Nusra Front, and others.

In December, Russian President Vladimir Putin ordered a “significant part” of Moscow’s military presence in Syria to begin withdrawing from the country, saying their objective had been achieved.

“Russia’s armed forces and the Syrian army have defeated the most battle-hardened group of international terrorists,” Putin said.

“The conditions for a political solution under the auspices of the United Nations have been created.”

Putin’s comments came a month after Assad thanked Putin for “saving” his country and for Russia’s support in Syria.