Russian President Vladimir Putin said on Saturday he remained "more positive than negative" over a shaky ceasefire in Syria, but a senior rebel in Aleppo warned the truce "will not hold out" as some fighting persisted and aid failed to come through.
The ceasefire is the result of an agreement between Russia, which backs Syrian President Bashar Assad with air power, and the United States, which supports some rebel groups, and has cooled fighting since coming into effect last Monday.
But in comments delivered in Kyrgyzstan on Saturday, Putin cast doubt over Washington's commitment to the deal, saying it was "deviating" from its own call for openness, and had been unable to split moderate from "semi-criminal" rebels.
However the two agreed on Friday to extend the ceasefire and Putin said that Russia would abide by its own commitments and still believed that securing a Syrian ceasefire was a common goal for both Washington and Moscow.
Insurgents say they only reluctantly accepted the initial deal, which they believe is skewed against them, because it could relieve the dire humanitarian situation in besieged areas they control, and blamed Russia for undermining the truce.
"The truce, as we have warned, and we told the (U.S.) State Department - will not hold out," the rebel official said, pointing to the continued presence of a UN aid convoy at the Turkish border awaiting permission to travel to Aleppo.
"It is not possible for the party (Russia) that wages war against a people to strive to achieve a truce, as it is also not possible for it to be a sponsor of this agreement while it bombs night and day, while on the other side, the other party - America - has the role of spectator," he said.
Moscow has itself accused rebels of breaking the truce and said Washington needs to do more to make them abide by its terms, including separating from the jihadist Jabhat Fateh al-Sham, which only broke formal allegiance to al-Qaida in July.
The five-year civil war has killed hundreds of thousands and displaced half the country's original population, drawing in global and regional powers, causing an international refugee crisis and inspiring jihadist attacks around the world.
Both sides have accused the other of being responsible for aid deliveries being stuck far from Aleppo, where army and rebel forces were supposed to retire from the Castello Road which leads into besieged, insurgent-held eastern districts.
Russia on Friday said the Syrian army had initially withdrawn but returned to its positions after being fired on by rebels, who in turn say they saw no sign of government forces ever leaving their positions.
"There is no change," said Zakariya Malahifji, an official for a rebel group in Aleppo on Saturday, asked whether there had been any move by the army to withdraw from positions along the road.
The United Nations pointed the finger at the government for holding up aid by denying letters guaranteeing access.
Warplanes strafed or bombed rebel-held areas in Maarat al-Numan, Saraqeb and Khan Sheikhoun in Idlib, Teir Maalah, north of Homs, and Souha, east of Hama, overnight after other strikes earlier on Friday, the Syrian Observatory for Human Rights said.
The Britain-based war monitoring group also reported clashes between the army and rebels or shelling overnight in the capital's Eastern Ghouta suburbs, in Sanaisil and Jawalik, north of Homs, al-Eis and Ramousah, south of Aleppo and Ibta in Deraa.
In the Jouba district of Damascus, clashes continued on Saturday after a large explosion and fighting on Friday, the Observatory said. It reported the two sides were shelling each other after what it said was an attempt by the army to advance.
Turkey-backed Free Syrian Army rebels are pushing south in northern Syria from the towns of al-Rai and Azaz towards the Islamic State-held town of al-Bab, supported by tanks and jets, security sources said, clashing with the jihadist group.
Vehicles were mobilized in northern Syria across from the Turkish village of Arapakesmez from the early hours of the morning and Turkish artillery deployed at the border have fired at Islamic State targets.
CNN Turk footage showed white smoke rising from across the border in Syria as Turkish howitzers fired west of al-Rai, where some U.S. special forces were briefly deployed to help coordinate against the militants before withdrawing on Friday.
If the ceasefire deal is successful, Moscow and Washington will start to share targeting information on militant groups, including Islamic State, they have said.
Elsewhere in Syria on Saturday, clashes resumed between the army, backed by air strikes, and Islamic State around the towns of Qasr al-Hair and Sukhna and the villages of al-Taiba and Arak, near Palmyra, the Observatory reported.
Jets also hit the group's positions near Deir al-Zor, while Islamist rebel groups including Jabhat Fateh al-Sham battled Islamic State fighters in the Eastern Qalamoun mountains northeast of Damascus.
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