DAMASCUS — Russia and a war monitor said the Syrian army had begun to withdraw from a road into Aleppo on Thursday, a prerequisite for pressing ahead with international peacemaking efforts as the government and rebels accused each other of violating a truce.

However, insurgent groups present in Aleppo said they still had not seen the army withdrawing from the Castello Road, needed to allow aid deliveries into the city, and would not pull back from their own positions near the road until they did.

The Pentagon said it could not confirm reports of a withdrawal but U.S. State Department spokesman Mark Toner said that the ceasefire was holding “by and large”, adding that both Washington and Moscow believed it was worth continuing.

But there were growing accusations of violations by each side, with a Syrian military source saying the rebels were responsible for dozens of breaches including gun, rocket and mortar fire in Damascus, Aleppo, Hama, Homs and Latakia. The rebels said Syrian army jets had struck in Hama and Idlib, and used artillery near Damascus.

The Syrian Observatory for Human Rights, a British-based war monitor, said that while it had documented attacks by both sides, relative calm had persisted in most areas and it had not recorded any civilian deaths for a third consecutive day.

Control of the Castello Road is divided between the government and rebels who have been battling to topple President Bashar al-Assad for more than five years. It has been a major frontline in the war.

The Observatory said the army had started to withdraw from positions on the road, but that Russian troops, whose air force has helped Damascus to blockade rebel-held Aleppo, had replaced it.

An official in an Aleppo-based Syrian rebel group said late on Thursday that the army had still not pulled back. “There is no withdrawal by the regime from the Castello Road,” Zakaria Malahifji, rebel group Fastaqim, told Reuters.

The U.N. Syria envoy Staffan de Mistura said the United States and Russia were expected to manage the disengagement of forces from the road, but also criticized Damascus for failing to provide permits needed to make aid deliveries to other areas.

The U.N. humanitarian adviser Jan Egeland said both the rebels and the government were responsible for delaying aid deliveries into Aleppo.