BEIRUT (AP) — Syria’s fragile cease-fire started to unravel on Sunday with the first aerial attacks on rebel-held neighborhoods of Aleppo and a southern village that killed at least eight people, violations that came as tensions between the American and Russian brokers of the deal worsened following a deadly U.S. strike on Syrian government forces.

The air raid by the U.S.- led coalition killed dozens of Syrian soldiers and led to a harsh verbal attack on Washington by Damascus and Moscow. The U.S. military says it may have unintentionally struck Syrian troops while carrying out a raid against the Islamic State group in eastern Syria on Saturday.

The seven-day cease-fire is supposed to end at midnight Sunday, according to a Syrian army statement issued last week. The U.S. and Russia have said that if it holds for seven days, it should be followed by the establishment of a Joint Implementation Center for both countries to coordinate the targeting of Islamic State and al-Qaida-linked militants.

Despite largely holding, the cease-fire has been repeatedly violated by both sides, and aid convoys have not reached besieged rebel-held neighborhoods of Aleppo, Syria’s largest city and one-time commercial center, which has been the center of violence in recent months. Aid delivery to Aleppo is part of the U.S.- Russia cease-fire deal.

Earlier this month, Syrian government forces and their allies captured areas they lost south of the city, re-imposing a siege on its opposition-held eastern neighborhoods. More than 2,000 people were killed in 40 days of fighting in the city, including 700 civilians, among them 160 children, according to a Syrian activist group.

Syrian state TV reported Sunday that dozens of residents had left rebel-held areas in Aleppo and were taken to shelters in the government controlled part of the city.

Also Sunday, Aleppo’s governor, Hussein Diab, called on insurgents in the eastern neighborhoods to turn themselves in, hand over their weapons and take advantage of an amnesty decree issued recently by Syrian President Bashar Assad.

“We are at a new stage that requires making the decision to embrace reconciliation,” Diab said in a statement carried by the state news agency, SANA. He urged insurgents to halt what he called the bloodshed and destruction and affirmed that all who turned themselves in and surrendered their weapons would be treated well and allowed to return to normal life.

Moscow laid the blame for Sunday’s violence squarely on the opposition. Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said in an emailed statement that both “terrorists and the opposition” are using the truce to “boost their forces and prepare for renewed hostilities.”

Konashenkov says Moscow still has not been able to contact the U.S.- backed opposition to coordinate cease-fire efforts despite Washington’s assurances. He said the U.S. has not even tried to get the opposition to hold its fire.

U.S. Secretary of State John Kerry fired back in an interview with CNN, saying Russia needs to stop Assad from attacking the opposition and blocking aid delivery.

Australian planes were also involved in the errant air raid. Defense Minister Marise Payne told Australian Broadcasting Corp. today that Australia is taking part in a U.S. review of the airstrikes. She declined to say whether Australia fighter jets were involved or support aircraft.

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