More than 400 civilians were among the 1,331 people killed in Russian airstrikes in Syria since September, a monitoring group said Friday.
The Syrian Observatory for Human Rights said the civilian toll included 97 children.
The overall toll is double that reported by the watchdog group three weeks ago.
It said 381 Islamic State militants were killed, along with 547 insurgents from Syria’s al-Qaeda branch, al-Nusra Front, and other rebel groups.
Russia, an ally of Syrian President Bashar al-Assad, says its airstrikes which began on September 30, are aimed at Islamic State and other extremist groups.
The Syrian opposition and its backers say Moscow’s actions have hit moderate rebels fighting both al-Assad and Islamic State.
Military jets, believed to be Russian, on Friday mounted at least 50 raids in the eastern province of Deir al-Zour, killing at least eight civilians, including three children, the Observatory said.
Russia has stepped up its airstrikes in Syria after Islamic State claimed responsibility for the October 31 downing of a Russian passenger airliner in Egypt.
The terrorist attacks in Paris on November 13 that killed 130 people and left more than 350 wounded were also claimed by Islamic State, prompting major world powers to intensify efforts for a political solution to the conflict in which more than 250,000 people have died in Syria since 2011.
Saudi Arabia said it will host a meeting next month for Syrian opposition groups to unify their ranks in the run-up to planned peace talks with al-Assad’s regime.
Ahmed Ramadan, a member of the Western-backed opposition Syrian National Coalition, welcomed the move and told dpa that a Saudi delegation was expected soon in Istanbul, where the coalition is based, to brief its leaders on the conference to be held in mid-December in Riyadh.
“The Saudi effort is aimed at confronting the Iranian and Russian interference in the Syrian crisis,” Ramadan said.
Russia and Iran have rejected repeated calls by the West and Saudi Arabia for al-Assad to step down to end Syria’s conflict.
Another Syrian National Coalition official said 30 Syrian rebel groups would attend the Riyadh meeting, including the Free Syrian Army and the Islamist factions of Jish al-Islam and Ahrar al-Sham.
Opposition groups inside Syria, which are tolerated by al-Assad’s regime, are also expected attend, he said.
Syria’s moderate opposition groups have been weakened by divisions, allowing jihadist rebels – mainly led by Islamic State – to establish a foothold.