John Bacon

USA TODAY

The second day of a Syria cease-fire agreement to allow humanitarian aid into towns battered by five years of brutal civil war was wobbly but generally holding Sunday, both sides said.

The complicated agreement brokered by the United States and Russia was approved by Western-backed rebels and the Syrian government. It does not involve attacks on the Islamic State or al-Qaeda's Syrian branch, Nusra Front, and the U.S. and Russia have continued bombing those targets.

Otherwise, the "cessation of hostilities," as it is formally called, began early Saturday, local time in Syria.

Both sides accused the other on Sunday of violations that could destroy the fragile deal and hamper hopes for peace talks. Russian Lt. Gen. Sergei Kuralenko said the cease-fire was generally observed, but he cited nine truce breaches. Russia asked the U.S. to review attacks from Turkey in the Syrian border town of Tal Abyad.

Syrian rebel leader Riad Hijab, who heads an umbrella group of rebel factions, claimed that Russian, Iranian and government forces had not stopped fighting. Hijab cited dozens of bombings and ground attacks and said it would be difficult to resume peace talks in Geneva next week if the violence is not curbed.

But Hijab also said it was "positive to see people getting relief … to be safe and free from fear," BBC reported.

Syrian war cease-fire is shaky from the start

The U.S. State Department pleaded for patience on both sides.

A State Department official told USA TODAY that the allegations are being treated seriously and urged all parties to practice restraint. The official, who declined to be identified because of the sensitivity of the issue, added that the U.S. and the United Nations are working to stem the violence as it arises.

The cease-fire got an encouraging start Saturday when reports indicated the capital of Damascus and the nearby rebel-held town of Daraya became calm. Opposition activists on the ground reported early adherence to the truce.

Russia's increased involvement in Syria with airstrikes has tipped the balance in favor of President Bashar Assad and complicated U.S. efforts to oust him and reach a political settlement to end the war. The toll has been high, with more than 250,000 people killed and millions displaced. That in turn has fueled the migrant emergency that has rolled deep into Europe.