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.
Australia's Department of Defense said in a statement that Australian aircraft were involved in the attacks in Deir Ezzor, targeting "what was believed to be a Daesh fighting position that the Coalition had been tracking for some time."
It said bombing "ceased immediately" once Russian officials notified the coalition's Combined Air Operations Center that the targets may have been regime forces.
Russia and Syria said the strikes prove Washington and its allies are sympathetic to ISIS, which they say was able to briefly capture a Syrian position in the wake of the coalition attack.
The Russian military says 62 Syrian soldiers were killed in the strikes, according to state media, while the UK-based Syrian Observatory for Human Rights put the death toll at 83, with at least 120 soldiers wounded.
US, Russia in war of words
On the sidelines of an emergency UN Security Council meeting called on the matter, tempers were high.
Russia's permanent UN representative, Vitaly Churkin, questioned the timing of the strikes, two days before Russian-American coordination in the fight against terror groups in Syria was to begin.
"I have never seen such an extraordinary display of American heavy-handedness," he said, after abruptly leaving the meeting.
Churkin was upset with US ambassador Samantha Power, who lambasted Russia's support of the Syrian regime to the media outside the meeting while he was speaking.
Power angrily denounced the Russian call for the UN meeting, saying "even by Russia's standards, tonight's stunt -- a stunt replete with moralism and grandstanding -- is uniquely cynical and hypocritical."
If US-led coalition airstrikes did hit Syrian forces Saturday, it was unintentional and Washington regrets any loss of life, she said, before proceeding to list atrocities she said the Syrian regime has perpetuated during the five-year civil war.
Russian Foreign Ministry spokeswoman Maria Zakharova responded to her remarks on Facebook, saying Power would understand "the meaning of the word 'shame'" if she visited Syria and met the people living there in "a bloody experiment, with the active involvement of Washington."
US: Coalition conferred with Russia
A statement from US Central Command said the coalition conferred with the Russian military before the strike.
"The coalition airstrike was halted immediately when coalition officials were informed by Russian officials that it was possible the personnel and vehicles targeted were part of the Syrian military," US Central Command said.
A US official told CNN they broadly described the geographic area to the Russians -- as is customary -- before the strike but did not give a precise location. The coalition thought it was going after an ISIS tank position.
"Syria is a complex situation with various military forces and militias in close proximity, but coalition forces would not intentionally strike a known Syrian military unit," CENTCOM said.
Russia blames the United States
Syrian troops have been battling ISIS for years in Deir Ezzor, where the Islamist militants control most of the city.
On Sunday, the Sunni terror group shot down a regime warplane involved in an anti-ISIS operation in Deir Ezzor province, killing the pilot, state-run SANA news agency reported, citing a military source. The terror group claimed responsibility for the shootdown in a statement circulated online by the ISIS-affiliated Amaq agency.
Russia blamed the United States for failing to coordinate with them on Saturday's airstrikes, a Russian Defense Ministry spokesman told Sputnik.
ISIS militants launched an attack on the Syrian position after the airstrikes, Sputnik reported, citing the Russian Ministry of Defense.
The SANA news agency said the military was able to quickly regain control of the area.
The Syrian military said it viewed the strike as evidence the United States and the coalition support ISIS. It called the incident a serious and blatant aggression, SANA reported. Russia's Foreign Ministry had similar words, according to spokeswoman Zakharova.
The latest ceasefire has offered some respite from violence in the civil war, which has killed an estimated 430,000 people since 2011 and touched off an international refugee crisis. But there have been numerous reports of violations, and both the Russians and Americans have said the other party is not fulfilling its obligations.
The main focus of the ceasefire was to allow humanitarian aid to reach the Syrian people. But nearly a week after the ceasefire began, desperate populations in besieged areas are yet to receive aid, which has been held up on the Turkish border as humanitarian agencies await guarantees of safety from the warring parties.
Once the humanitarian relief was in, the Russians and Americans were meant to agree on targeting jihadist factions: Jabhat Fateh Al-Sham, the former al Qaeda affiliate in Syria, and ISIS. To do that, they are supposed to set up a Joint Implementation Center.
CNN military analyst Lt. Col. Rick Francona said it is not clear now what will happen.
"This might put in danger this Joint Implementation Center that the US and the Russians are supposed to set up in the next few days to coordinate just these kinds of strikes against ISIS and to prevent just what happened," he said Saturday.