Tentative truce brokered by the US and Russia begins across Syria, but there are concerns about whether it will hold.
A nationwide ceasefire in Syria brokered by the United States and Russia began at sundown on Monday, coinciding with the Muslim Eid al-Adha holiday, but there are concerns about whether it will hold.
Several hours into the ceasefire, the UK-based Syrian Observatory for Human Rights (SOHR) said major conflict zones across the country were quiet.
"Calm is prevailing," said SOHR director Rami Abdulrahman, adding, however, that there had been light shelling by both rebel groups and government forces in the country’s southwest.
The deal, agreed to on Friday by US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov, aims at putting an end to fighting and moving towards a political transition after more than five years of war between forces loyal to President Bashar al-Assad and rebel groups fighting to depose him.
The truce does not apply to the Islamic State in Iraq and the Levant (ISIL), or Jabhat Fateh al-Sham, the group formerly known as al-Nusra Front that changed its name after cutting ties with al-Qaeda in July.
The Syrian government, as well as Iran and the Lebanese Hezbollah armed group, two of its strongest allies, have all agreed to the deal, but rebel groups expressed serious concerns.
Hours after the nationwide truce went into effect, more than a dozen rebel groups, including the Free Syrian Army (FSA) alliance, Ahrar al-Sham and Jaish al-Islam, put out a statement that harshly criticised the agreement, calling it "unjust", but stopped short of fully rejecting it.
The statement came a day after Ahrar al-Sham had denounced the deal in a video address.
At a State Department press conference two hours after the ceasefire came into effect, Kerry said there had been reports of violations "here and there", but urged all parties to adhere to the truce deal, saying it may be the last "opportunity" to obtain peace in a united Syria.
Hours before Monday’s truce was set to begin, Syria’s main opposition group and several rebel factions called for "guarantees" on the implementation of the ceasefire before fully endorsing it.
"We want to know what the guarantees are," said Salem al-Muslet, spokesman for the High Negotiations Committee, Syria’s main opposition bloc.
"What is the definition that has been chosen for ’terrorism’, and what will the response be in case of violations?" Muslet told AFP.
The FSA had said over the weekend that it would observe the truce, but had major reservations.
The alliance wrote to Washington on Sunday, saying that while it would "cooperate positively", it was also concerned that the deal would benefit the government of President Bashar al-Assad.
Just hours before the truce began, Assad said his government would take back all the land held by "terrorists" and rebuild the country.
After performing prayers for the Muslim Eid al-Adha holiday in the Damascus suburb of Daraya, once the heart of the uprising against the government and only recently surrendered by rebels, Assad vowed to "retake every inch of Syria from the terrorists".
In the lead-up to the sundown deadline, government air strikes hit rebel-held areas of Aleppo and Idlib on Monday, while Ahrar al-Sham pushed forward in a heavy offensive against pro-government forces in Quneitra in the country’s southwest.
"On the ground, what you see is more violence, more fighting and more air strikes," Al Jazeera’s Hasham Ahelbarra, reporting from Gaziantep on the Turkish side of the Syria-Turkey border, said.
Senior members said that they were "sidelined" by the deal and had "no guarantees about what will happen in the future, and that there is no indication about Assad stepping aside in the future," our correspondent reported.
Rebel commanders were also very concerned about the "targetting of the Nusra Front, which is a crucial component for the opposition in northern Syria," said Ahelbarra.
Alongside Ahrar al-Sham and other local factions, the group formerly known as Nusra forms the core of the Army of Conquest, which is credited for capturing the province of Idlib and breaking the siege on Aleppo.
In a letter sent to Syrian rebels ahead of the ceasefire, US State Department envoy Michael Ratney urged armed opposition groups to distance themselves from Jabhat Fateh al-Sham, or there would be "severe consequences".
According to the deal, aid access to the country’s many besieged and "hard-to-reach" areas is set to begin immediately, with government and rebel forces ensuring unimpeded humanitarian access, in particular to Aleppo city.
Questions remain, however, about how the ceasefire will apply in several parts of the country where Jabhat Fateh al-Sham is present.
If the ceasefire holds, the deal says that Washington and Moscow will begin joint targeting against hardline groups, including Jabhat Fateh al-Sham, in a week.
But the former al-Qaeda ally is a powerful partner for many opposition factions on the ground, and a rebel letter to the US over the weekend warned of repercussions if the group was targeted.
Striking Jabhat Fateh al-Sham, the rebels said, "will spark anger that will be directed towards us and be another factor in the failure of the ceasefire".
The letter, sent by FSA-related groups to the US on Sunday, outlined "concerns" over the deal.
In the text seen by AFP, rebels wrote they would "deal positively with the idea of the ceasefire," but did not explicitly back it.
"The clauses of the agreement that have been shared with us do not include any clear guarantees or monitoring mechanisms ... or repercussions if there are truce violations," they said.
Ahmad al-Saoud, who heads the US-backed Division 13 rebel group, a signatory of the letter, said they had received no response to their concerns.