Russia calls emergency U.N. meeting

The United States military said the coalition stopped the air strike against what it had believed to be Islamic State positions in northeast Syria after Russia informed it that Syrian military personnel and vehicles may have been hit.

Russia called for an emergency meeting of the United Nations Security Council after the air strikes, which allowed Islamic State militants to briefly overrun a Syrian army position near Deir al-Zor airport.

"We are reaching a really terrifying conclusion for the whole world: That the White House is defending Islamic State. Now there can be no doubts about that," the RIA Novosti news agency quoted Russian Foreign Ministry spokeswoman Maria Zakharova as saying.

She said the strikes threatened to undermine the ceasefire in Syria brokered by Russia, which has been aiding Syria's President Bashar al-Assad in the civil war, and the United States, which has backed some rebel groups.

The Russian Defence Ministry said U.S. jets had killed more than 60 Syrian soldiers in four air strikes by two F-16s and two A-10s coming from the direction of Iraq.

The Syrian Observatory for Human Rights, a Britain-based monitoring group with contacts across the country, cited a military source at Deir al-Zor airport as saying that at least 80 Syrian soldiers had been killed.

The ceasefire, which took effect on Monday, is the most significant peacemaking effort in Syria for months but has been undermined by repeated accusations of violations on both sides and by a failure to bring humanitarian aid to besieged areas.

As well as the U.S. and Russian involvement, Assad is supported by Iran and Arab Shi'ite militias, while Sunni rebels seeking to unseat him are backed by Turkey and Gulf Arab states.

All those warring parties are also sworn enemies of the Islamic State jihadist group, whose territory extends along the Euphrates valley from the Iraqi border, including around Deir al-Zor, up to land near Syria's frontier with Turkey.

In its sixth year, the conflict has cost hundreds of thousands of lives, displaced half of Syria's pre-war population, prompted a refugee crisis in the Middle East and Europe and inspired a wave of jihadist attacks across the world.

Syria's army said the strikes, which took place at around 5pm (1400GMT) were "conclusive evidence" of U.S. support for Islamic State, calling them "dangerous and blatant aggression".

The U.S. military said in its statement that Syria was a "complex situation" but that "coalition forces would not intentionally strike a known Syrian military unit".

Islamic State said via its Amaq news channel it had taken complete control of Jebel Tharda, where the bombed position was located, which would have allowed it to overlook government-held areas of Deir al-Zor.

The city's airport and some districts have been entirely surrounded by Islamic State since last year, with the airport providing their only external access.

However, Russia and Syrian state media said the Syrian army later recaptured positions it lost. The Observatory monitoring group said at least 20 Islamic State fighters were killed in heavy Russian air strikes during that fighting.

The incident threatens to undermine not only the ceasefire agreement, but also proposed joint targeting by the United States and Russia of Islamic State and some other jihadist groups across Syria.