The UK-based Syrian Observatory for Human Rights (SOHR) said Syrian fighter jets on Saturday bombed rebel positions in Hama.
The Britain-based war monitoring group said the warring sides exchanged shelling and were fighting in a rebel-held village and nearby areas of the Hama countryside. Under a memorandum signed at the talks in Astana, the four zones are Idlib province and some parts of neighboring provinces (Aleppo, Latakia and Hama), an area north of Homs, Damascus's suburb Eastern Ghouta, and a number of provinces in southern Syria - Daraa and Al-Quneitra.
The three governments agreed to the plan during a meeting on Friday in Kazakhstan, where peace talks in the capital of Astana have been ongoing.
U.S. Defense Department spokesman Major Adrian Rankine-Galloway told VOA on Friday that "we certainly welcome any effort, any worldwide effort to reduce the violence, to allow humanitarian assistance to reach those areas of Syria that need them, and ultimately a political resolution to the ongoing crisis there".
This photo provided by Azaz Media Office, a Syrian anti-government activist group, which has been authenticated based on its contents and other AP reporting, shows Syrian citizens and civil defense workers gathering next of burning vehicle at the explosion scene, in Azaz town, north Syria, Wednesday, May 3, 2017.More news: Putin supports plan to investigate reported abuse of gays
He said rebels doubted Russian or Syrian government warplanes would stop striking rebel-held areas after the deal takes effect.
Russia's military says the agreement setting up four de-escalation zones in Syria will go into effect. Adrian J.T. Rankine-Galloway.
U.S. State Department spokeswoman Heather Nauert said Thursday, before Russian Federation said U.S. -led coalition flights would also be restricted under the deal, that the United States had "reason to be cautious" about the chances for success of the deal, though it appreciates the efforts by Russian Federation and Turkey to help lower violence in Syria.
Russian Deputy Defence Minister Alexander Fomin said on Friday that there had been no bombing raids by Russian aviation in the four zones since 1 May. However, it is clear that the Astana agreement is a responsibility. She added that USA has concerns, including about Iran's "guarantor" role in the Kazakhstan deal.
The Pentagon said the de-escalation agreement would not affect the USA -led air campaign against IS.More news: LeBron leads Cavs in sweeping Pacers
It said the agreement "lacks the minimal elements of legitimacy" and also rejected any role for government ally Iran as a guarantor of the deal.
The areas where coalition flights would be banned include Idlib province, where USA warplanes have been carrying out a series of airstrikes against what officials say are al-Qaida operatives.
Russia, Turkey and Iran are to enforce the zones, but Russian general staff official Sergei Rudskoi said that other countries could participate.
The deal marks the latest diplomatic effort to quell the fighting.
Fighting has eased in parts of Syria where a Russian-led initiative to halt the country's six-year war took effect from midnight, activists say. After past failures, this deal provides for the first time a mechanism to observe the cease-fire: Russian, Iranian and Turkish troops are to monitor compliance on the ground.More news: Preds reach 1st Western final in team history, ousting Blues