The Syrian regime forces have declared a unilateral 72-hour "regime of calm" covering all of Syria from 1 p.m. (1000 GMT) on Wednesday, a military source told Reuters.
The military high command said in a statement that "a regime of calm will be implemented across all territory of the Syrian Arab Republic for a period of 72 hours from 1 p.m. on July 6 until 2400 on July 8, 2016". The announcement coincides with the Eid al-Fitr holiday marking the end of Islam's holy month of Ramadan.
The Free Syrian Army said on Wednesday it would abide by the ceasefire for the Eid holiday period.
"We, the armed revolutionary groups in Syria, welcome any effort towards a ceasefire for the happy Eid al-Fitr period. We declare we will abide by it so long as the other side does the same," said the statement, posted on the Twitter account of a prominent Syrian rebel figure.
The US and Russia brokered a nationwide ceasefire in February which held for a time but then collapsed under the pressure of localized fighting and a failed political process to end the violence.
There have been attempts since then to reach short-term cessations of hostilities that are often region-specific, but these have tended to be short lived.
Meanwhile, Bashar al-Assad joined Eid al-Fitr prayers at a mosque in third city Homs on Wednesday in a rare public appearance outside the capital for the end-of-Ramadan holiday.
Large parts of Homs were once under the control of opposition groups fighting to overthrow Assad's regime but since May 2014 they have been confined to a single besieged neighborhood in the city's outskirts.
The Al-Safa mosque, where Assad joined worshippers, is in Akrama, a loyalist neighborhood which has been hit by repeated attacks by the Daesh and its rivalling Al-Qaeda terrorist groups.
State television broadcast footage of the president in the congregation alongside Islamic Endowments Minister Mohammad Abdel-Sattar Sayyed and Syria's top Muslim cleric Ahmad Badredine Hassoun.
Since the civil war erupted in 2011, Assad has made only rare public appearances and nearly all of those have been in Damascus.