Syria's fragile ceasefire is under further threat after a series on new airstrikes in the country.

It comes amid a tense diplomatic spat between Moscow and Washington over four US-led airstrikes which mistakenly killed around 60 Syrian soldiers on Saturday.

America apologised for the bombing which occurred on a base near the eastern Deir al Zor airport, insisting their intended target was Islamic State fighters.

Russia's foreign ministry said the strike jeopardised the US-Russian brokered truce and accused the coalition of being on the "boundary between criminal negligence and direct connivance with Islamic State terrorists".

It added that the strike was a result of Washington's "stubborn refusal" to co-operate with Moscow in fighting Islamic State and other terror groups.


Meanwhile, the IS stronghold of Aleppo has been hit by its first aerial raids in nearly a week.

The barrage of airstrikes on the city's rebel-held districts risks reigniting battlefronts there and could be the most serious threat to the ceasefire so far.

In southern Syria, government helicopters dropped barrels bombs on a rebel-held village, killing eight people.

The Syrian military called the airstrikes on the base in Deir el Zour, which is surrounded by Islamic State militants, a "serious and blatant attack on Syria and its military" and "firm proof of the US support of Daesh (IS) and other terrorist groups".

Russia's defence ministry said more than 60 Syrian soldiers were killed and around 100 wounded in four strikes by two F-16s and two A-10s.

The two sides of Syria's war-torn Aleppo

A senior White House official said the US has relayed "regret" through the Russian government for the unintentional loss of life to Syrian forces.

US Central Command said the strike was immediately halted "when coalition officials were informed by Russian officials that it was possible the personnel and vehicles targeted were part of the Syrian military".

A US military official told Reuters news agency the strike was carried out using US intelligence, and added that the possible targets had been followed for days.

Australia has said its aircraft participated in the airstrike and offered its condolences to the families of Syrian soldiers killed or wounded.

The Syrian military said the damage caused by the strike has allowed the IS extremists to advance their position on to a hill overlooking the base.

Is the Syria ceasefire under threat?

Three tanks, three infantry fighting vehicles, four mortars and an anti-aircraft gun were destroyed, a Syrian military spokesman said according to Russia's TASS news agency reported.

Following the strike, the UN Security Council held an emergency meeting overnight at the request of the Kremlin.

The US ambassador to the UN, Samantha Power, rebuked Russia for the move.

"Russia really needs to stop the cheap point scoring and the grandstanding and the stunts and focus on what matters, which is implementation of something we negotiated in good faith with them," Ms Power said.

She said the US was investigating the airstrike and "if we determine that we did indeed strike Syrian military personnel, that was not our intention and we of course regret the loss of life".

When asked if the incident spelled the end of the Syria deal between Moscow and Washington, Russia's UN Ambassador Vitaly Churkin said: "This is a very big question mark.

"I would be very interested to see how Washington is going to react. If what Ambassador Power has done today is any indication of their possible reaction then we are in serious trouble."

He said he had never seen "such an extraordinary display of American heavy-handedness" as displayed by Ms Power at the acrimonious meeting.

The fragile ceasefire brokered by the US and Russia has largely held for five days, despite dozens of alleged violations on both sides.

It began on Monday, but aid convoys have been unable to enter rebel-held parts of the city of Aleppo - a key part of the deal.

Russian President Vladimir Putin has already questioned US commitment to the ceasefire, claiming Washington was not prepared to break with "terrorist elements" battling Bashar al Assad's forces.