Warring sides exchanged fire near Homs overnight, hours after a Russia-backed ceasefire in a safe zone took effect. Meanwhile, blasts near the cities of Aleppo and Raqqa signal rising tensions in northern Syria.
Warring sides exchanged rocket and gunfire north of the Syrian city of Homs overnight, hours after a Russia-backed truce took effect, a war monitor said on Friday, while heavy rocket fire also marred a similar deal east of the capital Damascus.
Russia, an ally of the Syrian government, said on Thursday its defence ministry and Syria's opposition had agreed to set up a "de-escalation" zone in the rebel-held countryside north of government-held Homs.
After an initial few hours of calm, the rebels and government forces and their allies began to target each other's territory. The monitor, the Britain-based Syrian Observatory for Human Rights (SOHR), said it had so far not received reports of any deaths.
The Russia-backed truce was similar to a de-escalation deal worked out in July for the besieged Eastern Ghouta rebel enclave east of Damascus.
Despite the deal and some reduction in violence, air strikes, rockets and exchanges of fire have continued to hit Eastern Ghouta.
The Observatory said since the Eastern Ghouta truce was declared on July 22 it had recorded at least 25 civilian deaths, including seven children, and dozens of injuries. Russia said it had deployed its military police in Eastern Ghouta in July to try to enforce the de-escalation zone.
Eastern Ghouta, the only major rebel-held area near the capital, has been blockaded by Syrian government forces since 2013. It has shrunk considerably in size over the past year as the Russia-backed Syrian regime army has taken control of other rebel-held areas around Damascus.
The SOHR said on Friday around 70 rockets had fallen in 24 hours on Eastern Ghouta in the heaviest bombing since the de-escalation zone was declared.
Several attempts at a lasting ceasefire in western Syria, where rebels have lost ground to government forces and their allies, have collapsed with both sides blaming the other for outbreaks of violence.
Blast targets Fateh al Sham office in Syria
Syrian opposition activists and state media say an explosion has targeted an office of an Al Qaeda affiliate in northern Syria, inflicting casualties.
Syrian regime television did not provide further details in its report. The SOHR says the explosion occurred near the office belonging to the Al Qaeda-linked Jabhat Fateh al Sham on Friday.
The SOHR says two of the group's fighters were killed and several others were wounded.
The Ibaa news agency, which is linked to Al Qaeda, says the blast in the village of Urum al Kubra, west of the northern city of Aleppo, left "several martyrs" and wounded people.
The explosion comes amid rising tension in northern Syria between various factions.
Daesh suicide attack in Raqqa
A Daesh suicide car bomb has killed and wounded dozens of US-backed SDF fighters in Raqqa.
The car bomb targeted a gathering of SDF fighters southwest of the city and destroyed a number of their vehicles. No deaths were reported.
At least eight civilians, one woman and seven children, have been killed in air strikes by the US led coalition, according to SOHR
The SDF is dominated by YPG, which is the armed wing of the PYD.
Ankara considers the PYD to be the Syrian branch of the PKK, which is recognised as a terrorist group by Turkey, the US and EU.
Heaviest clashes in months in Syria's Hama province
The heaviest fighting and shelling for months hit Hama province in northern Syria on Friday, the war monitor said, but there were diverging accounts of how the battle started.
The clashes were accompanied by heavy bombardment, with dozens of shells and rockets being fired, said the Syrian Observatory, adding that it had confirmed there had been casualties.
The battle is around the village of Maan, 23 km (15 miles) north of Hama in western Syria, near the location of a opposition assault and regime counter-offensive this spring.
The Observatory said the fighting arose from an attempt by pro-regime forces to advance north from Maan into opposition territory.
A military media unit run by the regime's ally Hezbollah, said it was opposition who tried to attack, but were thwarted by the Syrian regime army.
Groups like the Tahrir al Sham alliance are present in the area.
The war front in northern Hama province has mostly been quiet since a de-escalation process brokered by the regime's ally Russia and opposition-backer Turkey took effect in early May.
Refugees, fighters reach Syria after truce with Hezbollah
Nearly 8,000 Syrian refugees and fighters from Lebanon arrived in central Syria on Thursday as part of a ceasefire deal that also saw five Hezbollah fighters released, SOHR and Hezbollah said.
SOHR said the refugees and fighters arrived in bus convoys to a region held by opposition.
In return, Fateh al Sham released five fighters from Syrian regime ally Hezbollah, SOHR and Hezbollah's "War Media" outlet said.
The swap was part of a broader ceasefire deal announced last week between the two sides which ended six days of fighting in the mountainous Jurud Arsal region in the restive border area between Lebanon and Syria.
"The operation is now over," SOHR head Rami Abdel Rahman said.
"All five convoys of buses carrying fighters from Jabhat Fateh al Sham and [Syrian] civilians have reached the area" in central Hama province held by the opposition, he said.
As each convoy reached its destination, the group -- once known as Al Nusra Front and later as Fateh al Sham Front -- released one Hezbollah fighter, the Lebanese movement's "War Media" and SOHR said.
A source close to Hezbollah said the five fighters had been captured by the group during clashes in Aleppo province.
Dozens of trucks transported masked fighters who carried light weapons as well as Syrian civilian refugees, including women and children.