Fighting has stopped in three Syrian provinces after an open-ended ceasefire in southern Syria came into effect on Sunday according to the Syrian Observatory for Human Rights.

The ceasefire, brokered by the United States, Russia and Jordan, began at noon local time. The mechanisms to monitor or enforce the truce are not specified by any of the nations involved.

The agreement covers Daraa, Quneitra and Sweida provinces where the government and rebels are also fighting the militant Islamic State (IS) group, which is not included in the truce.

There has been no official comment from Syria's government on the announcement and there was no mention of the ceasefire on state television's noon news bulletin.

However, the Al-Watan newspaper, which is close to the regime, quoted the head of Syria's parliamentary Foreign Relations Committee suggesting that the agreement was negotiated in consultation with Damascus.

“No details on the agreement were presented, but the Syrian state has background on it,” the newspaper quoted Boutros Marjana as saying.

“The final word on adding southern Syria to the 'de-escalation' zones belongs to the Syrian state, and there is coordination with Russia on that,” he added.

The ceasefire is the first initiative by the American government in collaboration with Russia to bring stability to war-torn Syria.

It followed weeks of secretive talks in the Jordanian capital, Amman, to address the build up of Iranian-backed forces in support of the Syrian government near the Jordanian and Israeli borders.

“The main fronts in the three provinces between regime forces and opposition factions have seen a cessation of hostilities and shelling since this morning, with the exception of a few scattered shells fired on Daraa city before noon,” said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

A resident and local opposition activist, Ahmad al-Masalmeh, in Daraa, near the Jordanian border, reported calm in the opening minutes of the truce.

“There's still a lot of anxiety,” said al-Masalmeh. “We've entered the cease-fire but there are no mechanisms to enforce it. That's what concerns people.”

Russian Foreign Minister Sergei Lavrov had announced the ceasefire on Friday during a meeting between US President Donald Trump and Russian President Vladimir Putin.

Israel prime minister Benjamin Netanyahu said on Sunday that Israel would welcome a “genuine cease-fire” in southern Syria so long as it doesn't enable Iran and its proxies to develop a military presence along the border.

The Syrian regime had already announced its own unilateral ceasefire on Monday but fighting had continued on frontlines in the three provinces.

The ceasefire in southern Syria comes in the wake of a deal inked in the Kazakh capital Astana in May between regime allies Russia and Iran and rebel backer Turkey to set up four “de-escalation” zones.

On Friday, before the Russian foreign minister announced the ceasefire, a delegation of opposition factions that attended talks in Astana expressed opposition to any ceasefire for just one part of the country.

In a statement, the factions said they were concerned about “secret meetings and understandings between Russia, Jordan and America on a deal for the south of Syria, separate from the north.” The statement added that such an agreement, “would divide Syria, as well as the delegation and the opposition, in two.”

The ceasefire begins on the eve of fresh peace talks in Geneva scheduled to begin on Monday.

Expectations for the seventh round of UN-sponsored talks are low, but deputy to UN Syria envoy Staffan de Mistura, Ramzi Ezzedine Ramzi said Saturday that the ceasefire deal has created positive momentum.

“It helps create a suitable atmosphere for the talks, and we will see that on Monday,” said Ramzi.

No cease-fire has lasted long in the six-year-old Syrian war.