A lull in fighting was reported throughout Syria on Saturday, hours after a United States-Russia brokered "cessation of hostilities" agreement took effect amid hopes the truce will lead to an end of nearly five years of war.
The UN Security Council unanimously passed a vote late Friday to support the pause in fighting in Syria and demanded that all parties to the agreement fulfill their commitments to end hostilities.
The vote came less than an hour before the start of the proposed ceasefire, which began at midnight Damascus time on Saturday (22:00 GMT Friday).
Fighting had raged across much of western Syria right up until the agreement came into effect, the UK-based Syrian Observatory for Human Rights said.
"The situation is calm - the truce is largely holding - for the first time in many years. The airbase in Latakia, which the Russians use for their air strikes, was very calm, as well," said Al Jazeera's Omar al-Salah, reporting from Turkey's Gaziantep on the border with Syria.
An opposition activist in the Damascus suburb of Ghouta also reported quiet in the early hours of Saturday. Speaking shortly after midnight, Mazen al-Shami told AP that "Eastern Ghouta is quiet for the first time in years".
While there were no reports of air strikes or heavy artillery fire, violence was reported on Saturday.
A Syrian rebel group in the country's northwest said it came under attack from government ground forces at 4am (02:00 GMT) in what it called a breach of the cessation of hostilities plan.
Three fighters from the rebel First Coastal Division were killed while repelling the attack in the Jabal Turkman area near the Turkish border in Latakia province, Fadi Ahmad, the group's spokesman, told Reuters news agency.
The Syrian military could not immediately be reached for comment.
The Syrian government has said it will respect the agreement drawn up by Russia and the United States, but said it will continue to fight the al-Qaeda-linked al-Nusra Front and the Islamic State of Iraq and the Levant (ISIL) group, which are not covered by the deal.
Meanwhile, a suicide car bomb exploded Saturday on the edge of Salamiyeh, a government-held central town, killing two people and wounding four others, the state news agency said.
UN Syria envoy Staffan de Mistura said any use of force must be proportionate and as a last resort if fresh fighting breaks the cessation of hostilities. "No doubt, there will be no shortage of attempts to undermine this process. We are ready for it," he said.
Countries backing the Syrian peace process meet on Saturday in Geneva to assess the situation.
"Let's pray that this works because, frankly, this is the best opportunity we can imagine the Syrian people has had for the last five years in order to see something better and hopefully something related to peace. Facts will tell," de Mistura said.
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Al Jazeera's diplomatic editor, James Bays, reporting from UN headquarters in New York, said the start of the conditional truce was a crucial moment in the peace process.
"Everyone knows there are going to be violations of the cessation of hostilities," he said.
"Diplomats tell me the best they can expect is a lull in the violence. And then it might just be possible to persuade the warring parties to resume talks in Geneva."
De Mistura said Syrian peace talks will reconvene on March 7 if the ceasefire holds.
The opposition alliance, known as the High Negotiations Committee (HNC), said in a statement that 97 factions and armed groups fighting the forces of President Bashar al-Assad will respect the two-week truce.
The Syrian government has previously said it would abide by the truce, but would have the right to retaliate for any attacks.
The deal marks the biggest diplomatic push yet to end Syria's nearly five-year-old war, which has killed more than 260,000 people and displaced millions from their homes.
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Source: Al Jazeera and agencies