Human rights groups accuse Russia of killing thousands of people in Syria, but the Kremlin claims it has killed even more.

On the third anniversary of Russia’s military intervention in Syria, an independent monitoring group, the Syrian Observatory for Human Rights, said Russian air strikes and artillery shells have killed 18,000 people, including nearly 8,000 civilians, .

The Syrian Network for Human Rights, another monitoring group, alleged 6,239 civilians have been killed, including 1,804 children at the hands of Russian forces, according to a 40-page report it issued on Monday.

But the Kremlin says it killed significantly more in its quest to bolster the rule of Bashar al-Assad in Syria. The head of its parliamentary defence committee announced on Sunday that it had killed 85,000 people, calling them all “terrorists”. Russia also claims it has not killed a single civilian in Syria over the last three years.

A total of 112 Russian military personnel have been killed in Syria over the last three years, not counting hundreds of private contractors killed in a US air strike last year.

Viktor Bondarev, head of the parliamentary defence and security committee, said the sacrifices were worthwhile since they prepared Russia for future battles and taught the armed forces to fight.

“The most important criteria of military prowess is not just the victory but also its price,” he said, according to the Interfax news agency.

The September 2015 Russian intervention in Syria changed the course of the war, tipping the balance strongly in favour of the pro-Assad forces at a time when rebels were seen to be winning the conflict. But Russia has also been accused of inflicting horrific attacks on Syrian civilians, with human rights monitors accusing it of indiscriminately bombing populated areas, and targeting hospitals in an attempt to degrade life in rebel-held territories.

The White Helmets, a rescue group funded by US, UK and other western countries, issued a report on Sunday also accusing Russia of disregarding truce and de-escalation deals it itself helped broker over the last three years.

The report by the Syrian Network for Human Rights, which is close to the opposition, accused Russia of culpability in war crimes, including 321 mass-casualty incidents and 954 attacks on civilian infrastructure such as schools, medical facilities, and markets. The Pentagon last week admitted it had killed at least 1,100 civilians while fighting Isis in Iraq and Syria.

The three-year anniversary of the Russian intervention comes as the Kremlin seeks to wrap up the conflict. Russia struck a deal with Turkey last month to stave off an impending attack on the rebel-held Idlib province. That deal​ included the establishment of a demilitarised buffer zone between opposition and government forces that would be devoid of fighters and heavy weapons.

In recent days, the successor to the Syrian branch of al-Qaeda has begun rounding up foreign fighters in Idlib. Hayat Tahrir al Sham (HTS), a coalition of rebel fighting groups that includes the successor to the al-Qaeda-controlled Jabhat al-Nusra, has reportedly arrested dozens of non-Syrians within its ranks, according to jihadis on social media. .

Prominent al-Qaeda supporters online said HTS arrested around 34 foreign fighters, accusing the group of betraying the jihadi cause and acceding to demands by Turkey, which has emerged as the primary patron of the Syrian opposition to Assad’s rule.

But others say the detentions could just be part of internal convulsions within HTS, which is riven by factions.

“What’s happening in regards to arresting and even the assassination of specific fighters is not a new thing,” said Nawar Oliver, a researcher at the Omran Institute for Strategic Studies, an Istanbul think tank.