Minor violations reported as crucial cease-fire holds

It's the second attempt this year to try to reduce violence that has seen more than 250,000 killed

The cease-fire in Syria appeared to be holding on Tuesday despite sporadic and minor violations, with observers saying most of the country was calm amid the latest attempt by the United States and Russia to bring some quiet in the country's devastating civil war, now in its sixth year.

The deal, hammered out by US Secretary of State John Kerry and his Russian counterpart Sergey Lavrov last week in Geneva, officially came into effect at sunset on Monday. The Syrian army announced at the time that it would abide by the cease-fire until midnight on Sunday, while maintaining its right to defend itself against any violations.

It's the second attempt this year to try reduce violence in war-torn Syria where the conflict has killed more than 250,000 people and displaced half the country's population of 11 million. A truce in late February collapsed just days later.

The first week of the truce will be crucial. During that time, all warring sides in Syria need stop attacks and airstrikes, and allow access to besieged areas, including the northern city of Aleppo.

It also includes improving humanitarian aid access and a joint military operation against banned terrorist groups.

If calm holds for seven days, the US and Russia would then set up a new cooperation center that would jointly develop strategies to combat the al-Qaida-linked group formerly called the Nusra Front and now known as Jabhat Fatah al-Sham.

Under the truce, the government forces are no longer supposed to bomb Syria's opposition.

For the moment, "calm is prevailing in all areas," said Ahmad al-Masalmeh, an opposition activist in the southern province of Daraa - where Syria's crisis began in 2011.

In the northern city of Aleppo, where the fighting has concentrated over the past few months, opposition activists said rebel-held parts of the city were calm on Tuesday morning but many people were still hunkering down in their homes, fearful of going out. Aleppo-based activist Baraa al-Halaby said no aid deliveries, which are also part of the cease-fire deal, have entered the contested area.

Rebels fire three shells

Syrian state news agency SANA said rebels fired three shells at a government-held neighborhood in Aleppo.

Ibrahim Khalil, a 43-year-old father of two, said he doesn't believe in the truce.

"We are against the truce, because whenever there is a truce, the rebels start recollecting themselves and amassing weapons and manpower again and they shell Aleppo again. Every time there is a truce, the people are the ones who pay the price," he said, trying to end the conversation as he feared another mortar would hit soon.

The deal's architects hope the cease-fire will pave the way for an extended period of restraint that can serve as the foundation for peace talks.

As the cease-fire came into effect, Kerry on Monday also urged Syrian rebel factions to distance themselves from al-Qaida-linked militants.

In other developments, the Syrian military announced its forces on Tuesday shot down two Israeli aircraft - a warplane and a drone - near the Israeli-controlled part of the Golan Heights. The Israeli military quickly denied the Syrian claim.

The Israeli military said "two surface-to-air missiles were launched from Syria after the mission overnight to target Syrian artillery positions" but that the safety of Israeli planes was not compromised.