BEIRUT — The second day of a partial truce in Syria was marred on Sunday by a number of airstrikes and artillery attacks, the warring sides reported, demonstrating the challenges of even a limited deal.

The Syrian government and opposition, and their respective supporters, accused each other of violating the truce, a tit for tat of allegations that is likely to continue, because there is no independent monitor or clearly established mechanism for deciding what constitutes a violation.

Several airstrikes, by the Syrian government or its Russian allies, struck insurgent-held areas in the provinces of Aleppo, Hama and Idlib, according to insurgent groups and civilian activists who posted videos online.

The Syrian opposition called the attacks violations of the truce, saying that they had targeted insurgent groups other than the al-Qaida-linked Nusra Front and the Islamic State, two organizations that were excluded from the deal.

At the same time, Russian officials announced that there had been nine violations by opposition groups and Turkish allies in the first 24 hours of the truce.

The officials cited shelling attacks by insurgents on Damascus as well as Turkish artillery fire across the border into Tal Abyad, where Kurdish militias were battling the Islamic State, also known as ISIS or ISIL.

In one of the conflict's many contradictory twists, Turkey considers the Kurds its most dangerous enemies in the region, even as the United States, a NATO ally of Turkey, works with Kurdish militias to battle the Islamic State.

Several government or Russian airstrikes were carried out over areas that are considered crucial fronts. Two airstrikes hit houses in Jisr al-Shughour in Idlib province, a critical region that government forces are trying to take back from insurgents who seized it a year ago.

According to the White Helmets, a civil defense group, one strike killed a pregnant woman and wounded 12 others, including seven children.

Yet in many areas, Syrians continued to say they were pleasantly surprised that the cease-fire deal — of which all sides had voiced low expectations — had led to a couple of days of relative calm.

In the Damascus suburbs, residents said they were surprised to hear no airstrikes on Daraya, long a hub of rebellion. Syrian officials had declared that Daraya would be exempt from the cease-fire and that they would keep attacking it, even as opposition groups insist it is controlled by rebels who do not belong to the Nusra Front or the Islamic State.

But strikes on the suburb appeared to have temporarily stopped on Sunday, leading some residents to express hope that Russia was prevailing on its Syrian allies to show goodwill under the truce.