Nearly 600 people, the majority of whom were rebels, were killed by Moscow attacks in last month, monitoring group says.
Russia’s air force chief says Moscow has sent anti-aircraft missile systems to Syria to back its campaign of air strikes in the country.
Viktor Bondarev said in an interview published by a Russian newspaper on Thursday that the air-defence systems would be used to prevent potential air attacks on its troops in Syria, who are backing government forces against opposition groups.
Bondarev told the Kosmsomolskaya Pravda paper that Russia “took into account every possible threat” when making the decision to deploy the weapons.
“There could be various force majeur situations. Let us imagine a military plane is hijacked and taken to a neighbouring country and air strikes are aimed at us. And we have to be ready for this,” he said.
Bondarev said Russia has “more than 50 planes and helicopters” in Syria.
The statement came amid Moscow’s efforts to restart peace talks between the Syrian government and opposition groups.
The Russian news agency Sputnik reported on Thursday that the Free Syrian Army (FSA), a main umbrella group of opposition fighters, had agreed to meet Russian officials in Abu Dhabi, the capital of the United Arab Emirates.
Sputnik quoted Mahmoud al-Adandi, the coordinator of the dialogue, as saying that the FSA delegation, comprised of representatives from 28 brigades, would hold talks with Russian foreign and defence ministry officials.
Adandi also reportedly said that the meeting would discuss the creation of a joint operating centre to fight the Islamic State of Iraq and the Levant (ISIL) and al-Nusra Front, a Syrian armed opposition group.
However, representatives of four FSA groups dismissed the report.
Bashar al-Zoubi, a prominent rebel figure, said there was no sign that the Russians wanted an “honest solution” to the war, and therefore there was no contact with them.
Zoubi, who is head of the political office of the FSA-affiliated Yarmouk Army, added that he had not heard anything of the meeting.
Fares al-Bayoush, head of another FSA group, Fursan al Haq, also said no FSA delegation was going to meet the Russian officials.
“They are meeting with Syrians who do not represent anyone, and claim they met representatives of the Free Army,” he said.
A member of the FSA-affiliated Sham Revolutionary Brigades’ leadership council, as well as the head of the FSA group 13th Division fighting in western Syria, echoed the denials.
At least 50 people were reportedly killed and others were injured on Thursday after Russian warplanes bombed a market in the centre of al-Bukamal in eastern Syria.
The town, which borders Iraq, has been under ISIL control since last summer.