The diplomatic dispute heated up on the last day of a seven-day ceasefire marred by a surge of violence as warplanes hit the strategic northern city of Aleppo for the first time since the truce came into effect, according to Reuters.
In another blow to hopes for the ceasefire, the governor of Homs said several hundred rebels would be evacuated from the last rebel-held district of the Syrian city on Monday, prompting rebels to warn any such step would amount to the government declaring the end of the truce.
On Saturday, the Russian Defence Ministry said U.S. jets had killed more than 60 Syrian soldiers in the eastern Syrian city of Deir al-Zor in four air strikes by two F-16 and two A-10 fighter jets coming from the direction of Iraq, according to the report.
Syrian U.N. Ambassador Bashar Ja'afari charged that U.S.-led strikes were aimed at torpedoing the ceasefire but France's foreign minister, speaking in New York, placed the main blame for truce violations on President Bashar al Assad's government.
The Britain-based monitoring group Syrian Observatory for Human Rights said a military source at Deir al-Zor airport reported at least 90 Syrian soldiers were killed in the strikes.
"The actions of coalition pilots - if they, as we hope, were not taken on an order from Washington - are on the boundary between criminal negligence and connivance with Islamic State terrorists," Russia's Foreign Ministry said in a statement.
Read alsoReuters: U.S.-led forces strike Syrian troops, prompting emergency U.N. meeting"We strongly urge Washington to exert the needed pressure on the illegal armed groups under its patronage to implement the ceasefire plan unconditionally. Otherwise the implementation of the entire package of the U.S.-Russian accords reached in Geneva on Sept. 9 may be jeopardized," it said.