A U.S.-Russian brokered ceasefire for southwest Syria was holding hours after it took effect on Sunday, a monitor and two rebel officials said, in the latest international attempt at peace-making in the six-year war.

The United States, Russia and Jordan reached a ceasefire and "de-escalation agreement” this week with the aim of paving the way for a broader, more robust truce.

The announcement came after a meeting between U.S. President Donald Trump and Russian President Vladimir Putin at the G20 summit of major economies in Germany.

‘Relatively calm’

The Syrian Observatory for Human Rights, a Britain-based war monitoring group, said “calm was prevailing” with no airstrikes or clashes in the southwest since the truce began at noon (0900 GMT) on Sunday. “The situation is relatively calm,” said Suhaib al-Ruhail, a spokesman for the Alwiyat al-Furqan rebel group in the Quneitra area.

Another rebel official, in Deraa city, said there had been no significant fighting. It was quiet on the main Manshiya front near the border with Jordan, which he said had been the site of some of the heaviest army bombing in recent weeks. A witness said he had not seen warplanes in the sky or heard any fighting since noon.

A Syrian official indicated that Damascus approved of the deal, describing the government’s silence over it as a “sign of satisfaction”.