The Syrian Observatory for Human Rights said major conflict zones in Syria were calm after a ceasefire took effect at 7 p.m. (1600 GMT) on Monday.
“Calm is prevailing,” Observatory Director Rami Abdulrahman told Reuters, giving an early assessment of the impact of the agreement brokered by the United States and Russia.
He said there had however been some shelling by both rebel and government forces in the southwest of the country.
The Observatory gathers its information from a network of sources in Syria.
He told reporters at the State Department that it was too early to draw a definitive conclusion about how effective the truce will be, and that there would no doubt be some reports of violations “here and there.”
Russia has also expressed concern over the Islamist militant group Ahrar al-Sham not pledging commitment to the ceasefire.
Moscow added it was counting on the US to influence “moderate opposition” in Syria to ensure full compliance to the truce.
“The Syrian state is determined to recover every area from the terrorists,” Assad said in an interview broadcast by state media, flanked by his delegation at an otherwise deserted road junction.
He made no mention of the ceasefire agreement, but said the army would continue its work “without hesitation, regardless of any internal or external circumstances.”
The ceasefire was due to take effect at sundown, and includes improved humanitarian aid access and joint US and Russian targeting of hardline Islamists. But it faces big challenges, including how to separate nationalist rebels from the jihadists.
The rebels say the deal benefits Assad, who appears stronger than at any point since the early days of the war, with military support from Russia and Iran.
The capture of Daraya, a few kilometers (miles) from Damascus, followed years of siege and bombardment and has helped the government secure important areas to the southwest of the capital near an air base.
Backed by Russian air power and Iranian-backed militias, the army has also completely encircled the rebel-held half of Aleppo, Syria’s largest city before the war, which has been divided into government and opposition-held zones for years.
In the footage of his visit to Daraya, Assad, 51, appeared to be driving his own vehicle, a silver SUV, as he arrived at the mosque. He smiled and waved as he entered.
“The decision is taken,” the opposition source said, speaking on condition of anonymity. “In the next few hours there will be a statement where we state that, but there will be a lot of harsh reservations and observations regarding the whole package. But as a final takeaway, we do agree.”
The source said the acceptance had already been communicated to the United States, which finalized the proposed package with Russia on Friday.
The statement will be backed by “the largest groups,” including Ahrar al-Sham, a militant group that had vocally criticized the deal, the source said.
The terms of the deal mean that if the peace holds for about nine days, Syria’s air force will be sidelined and joint US-Russian strikes will begin against militant groups that are banned from taking part in the truce – ISIS and Jabhat Fateh al-Sham, which was until recently called the Nusra Front.
“Targeting Fateh al-Sham and treating it in a different way to the (Iran-backed) Shiite militia, and pushing us or expecting us to agree to a package where part of it is to bomb them, is going to create a lot of internal problems, and it’s already happening on the ground, and there’s a lot of tension,” the opposition source said.
“We want to cancel out any possibility of internal confrontation by clearly stating that we do not agree or endorse the idea of targeting Fateh al-Sham because the other side does have other groups that fit the designation criteria, but they are acting freely and with coverage inside Syria.”
Armed groups would continue to operate with Jabhat Fateh al-Sham, the opposition source said, because it was impossible to disentangle the forces that fought side by side.
“From our point of view it’s business as usual,” the source said, adding that it was unclear how the United States and Russia planned to cooperate on targeting the banned militants.
Russia’s intervention in the Syrian war a year ago has tilted it in Assad’s favor, after rebel advances had posed a growing threat to his rule. It has also given Russia decisive leverage over international diplomacy that has thus far failed to make any progress towards a political settlement.
The Russia-US deal is the second attempt to bring about a ceasefire this year, after an agreement concluded in February collapsed as each side blamed the other for violations.
Washington, which supports some rebel factions, has been seeking to refocus the fighting in Syria on ISIS, which still controls swathes of the country and has not been included in any ceasefires.
Fighting raged on several key frontlines on Monday, including Aleppo and the southern province of Quneitra.
“There are no signs we are going to a truce so far,” said Rami Abdulrahman of the Syrian Observatory for Human Rights, which monitors the conflict.
The Syrian war has killed hundreds of thousands of people and forced 11 million people from their homes in the world’s worst refugee crisis. The new truce has official support from countries on both sides, including both Iran, Assad’s ally, and Turkey, a major sponsor of the insurgency against him.
During this time, opposition fighters will have the chance to separate from militant groups in areas such as Aleppo.
But distinguishing rebels protected by the ceasefire from militants who are excluded from it is tricky, particularly with regards to Jabhat Fateh al-Sham.
The United States has said the deal includes agreement that the government will not fly combat missions in an agreed area on the pretext of hunting fighters from the former Nusra Front. However, the opposition says a loophole would allow the government to continue air strikes for up to nine days after the ceasefire takes effect.
Nationalist rebel groups, including factions backed by Assad’s foreign enemies, wrote to Washington on Sunday to express deep concerns over the truce. The letter, seen by Reuters, said the opposition groups would “cooperate positively” with a ceasefire but believed the terms favored Assad.
It said the ceasefire shared the flaw that allowed the government to scupper the previous truce: a lack of guarantees, monitoring mechanisms or sanctions against violators.
It also said Jabhet Fateh al-Sham should be included in the truce, as the group had not carried out attacks outside Syria despite its previous ties to al-Qaeda. Jabhet Fatah al-Sham said the deal aimed to weaken the “effective” anti-Assad forces, and to “bury” the revolution.
The government has made no comment on the agreement, but Syrian state media quoted what it called private sources as saying the government had given its approval.
The previous cessation of hostilities agreement resulted in a UN-led attempt to launch peace talks in Geneva. But these broke down before getting started in earnest.
Russian Deputy Foreign Minister Mikhail Bogdanov said a new round of talks between the Syrian government and opposition may be held in early October, the RIA news agency said.
“I think that probably at the very beginning of October (UN Syria envoy Staffan) de Mistura should invite all the parties,” Bogdanov was quoted as saying.