A nationwide ceasefire in Syria brokered by Russia and Turkey was in effect early on Friday, a potentially major breakthrough in the nearly six-year conflict, despite reports of isolated clashes.
While the truce was standing in most parts of the country, some fighting broke out near a Christian town in central Hama province between rebels and Syrian government, according to a monitoring group.
"Fierce clashes took place between the two sides pushing regime forces to withdraw from a hill near Maharda," Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights, told AFP news agency.
"Small rebel groups and armed loyalists are seeking to destroy the truce because it puts an end to their presence," he said.
In a report on Thursday, the monitor said major provinces witnessed "a calm atmosphere" in the first hours of the ceasefire.
Elsewhere, the Turkish military said on Friday that Russia carried out three air strikes against the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group near al-Bab, killing at least 12 ISIL fighters.
At least one Turkish soldier was killed in an attack on ISIL in northern Syria, Turkey's army added, claiming that its air strikes killed another 26 ISIL fighters in al-Bab and Daglabash. ISIL is excluded from the ceasefire.
The ceasefire agreement, hailed by Syria's government as a "real opportunity" to find a political solution to the war, comes a week after government forces recaptured the city of Aleppo in a major blow to rebel forces.
Russia and Turkey back opposing sides in the conflict, and the ceasefire does not involve the United States, which has negotiated previous ceasefires with Moscow.
A statement carried on Thursday by Syria's state news agency SANA said the truce, as well as excluding ISIL, also leaves out fighters from Jabhat Fateh al-Sham, and "groups linked to them".
Al Jazeera's Charles Stratford, reporting from Gaziantep on the Turkish border with Syria, said "there are high hopes that this [truce] might work, but there are huge potential problems with it. The biggest seems to be this group - Jabhat Fateh al-Sham".
"There are fears that if there are air strikes targeting" Jabhat Fateh al-Sham, which has often fought alongside a number of signatories to the agreement, "then there may be some casualties" among those factions as well.
Russian Defence Minister Sergei Shoigu said seven opposition groups, including the powerful Ahrar al-Sham, had signed the deal and those who failed to adhere would be considered "terrorists".
Usama Abu Zeyd, the Free Syrian Army (FSA) spokesman, said that the rebels had held no direct talks with the Syrian government or Iran during the truce talks and insisted that President Bashar al-Assad would have no place in the future of Syria.
"The ceasefire covers all the territories of Syria and it extends to include all the groups fighting under the Syrian armed opposition," he said, adding that the rebels had agreed to start peace talks.
The agreement comes after Turkey and Russia also brokered a deal to allow the evacuation of tens of thousands of civilians and rebel fighters from Aleppo.
"Now we need to do everything for these agreements to come into force, for them to work, so that the negotiating teams that have been or are being formed promptly and as soon as possible arrive in Astana," Russian President Vladimir Putin said.
United Nations peace envoy Staffan de Mistura said he hoped the agreement would "pave the way for productive talks" in Kazakhstan, but also reiterated he wants negotiations mediated by his office to continue early next year.
Turkey has long backed Syria's opposition, and its relations with Russia soured last year after Ankara shot down a Russian warplane.
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But the two countries have worked closely of late on Syria, and Turkey was conspicuously quiet as Assad's forces retook Aleppo.
Syria's civil war, which began when a peaceful uprising descended into violence in 2011, has, according to the UN resulted in more than 400,000 deaths and displaced over 11 million people, half its prewar population.
The ceasefire, in the waning days of President Barack Obama's administration, was the first major international diplomatic initiative in the Middle East in decades not to involve the US.
Source: Al Jazeera and news agencies