Story highlights

Australia says its warplanes were among a number of international aircraft in Saturday's operation

ISIS shot down a regime warplane in Deir Ezzor, killing a pilot, Syrian state media says

CNN  — 

One day after coalition airstrikes bombed Syrian government troops, warplanes made multiple attacks against rebel strongholds in eastern Aleppo on Sunday.

Sunday’s strikes turned up the pressure on a fragile ceasefire brokered between Washington and Moscow, now in its sixth day, and make the cloudy situation in war-torn Syria even grayer.

It was not known who conducted Sunday’s strikes, which the Syrian Observatory for Human Rights said were the first in Aleppo since the US-Russia-backed ceasefire took effect last Monday. At least one woman has died and many people have been wounded, some critically.

Russia has said the US-led coalition airstrikes that mistakenly killed dozens of Syrian troops on Saturday – prompting a diplomatic firestorm – put the ceasefire in jeopardy.

The strikes near Deir Ezzor Airport – which the US says were intended to target ISIS but instead killed 62 Syrian soldiers, according to the Russian military – sparked a furious row between the US and Russian ambassadors to the United Nations outside an emergency Security Council meeting.

The US has expressed regret for the strikes, while Australia, which says its planes were among a number of international aircraft involved in the operation, expressed condolences to the victims’ families.

“We consider what happened as a natural result of the persistent refusal of the United States from the establishment of close cooperation with Russia in the fight against ISIS, Jabhat al-Nusra and other affiliated terrorist groups,” the Russian Foreign Ministry said in a statement.

Bouthaina Shaaban, a political and media adviser to Syrian President Bashar al-Assad, told CNN’s Becky Anderson that Syria is adhering to the truce and the US should start cooperating.

“I ask the United States if they truly mean to target terrorists, where is the problem in coordinating their efforts with Russia, with the Syrian-Arab army, with anyone who is targeting terrorists?” asked Shaaban.

“After all, this is the target for all of us, so why are they prolonging the agony of the Syrian people and allowing the terrorists, all this time, and all this space, to slaughter our people?” she said.

US regret for ‘unintentional loss of life’

The strikes occurred Saturday in a part of eastern Syria that is not covered by the ceasefire. The US military acknowledged having carried out the strikes, but said they was targeting ISIS militants and that if strikes hit Syrian troops, it was by accident.

The US “relayed our regret through the Russian Federation for the unintentional loss of life of Syrian forces fighting ISIL,” a senior US official told CNN late Saturday, adding that the US would continue to pursue compliance with the ceasefire agreement while targeting terror groups like ISIS, which are not covered by the truce.