BEIRUT (AFP) - Tens of thousands have returned to their homes in southern Syria since a ceasefire deal between regime ally Russia and rebels to end more than two weeks of deadly bombardment, a monitor said Sunday (July 8).

The deal was largely holding despite air strikes on two areas that killed four civilians, the Syrian Observatory for Human Rights monitoring group said, as rebel evacuations under the deal were postponed.

President Bashar al-Assad's regime is determined to retake control of the key southern province of Daraa bordering Jordan and the Israeli-occupied Golan Heights, seven years after protests there sparked Syria's civil war.

Since June 19, a deadly regime bombardment campaign on the province had caused more than 320,000 people to flee their homes, according to the United Nations, many to the sealed border with Jordan.

On Friday, rebels and the regime announced a ceasefire deal, providing for opposition fighters to hand over their heavy weapons and paving the way for a regime takeover of the province.

More than 60,000 people have since hit the road from the Jordanian frontier, heading back to their homes in the east or west of the province, the Britain-based Observatory said.

On Sunday, the returns were continuing, the Observatory said, even as regime warplanes pounded two areas of the province.

Three civilians were killed in air strikes on Um al-Mayazeen, just five kilometres north of the Jordanian border, said the Britain-based monitor.

"Regime forces launched an assault on the village," Observatory director Rami Abdel Rahman said, two days after they retook control of the key border crossing of Nassib to its south.

Earlier, rebel fire on a regime convoy travelling near Um al-Mayazeen on the highway from the border had killed several soldiers, Abdel Rahman said, without providing a toll.

A regime air strike on the rebel-held half of the provincial capital of Daraa also killed one civilian, he said.

On Friday, regime forces retook control of Nassib, near which thousands of families had set up makeshift tents for shelter.

Under the ceasefire deal, regime forces were to deploy along the frontier with Jordan, while rebels were to hand over their heavy weapons.

Opposition fighters were also given the option of being bused out to rebel-held areas in northern Syria.

But a rebel official said the evacuation of opposition fighters and their families planned for Sunday was temporarily put on hold.

"A hundred buses were supposed to arrive but (the operation) has been postponed to a later date, in around two days," the official said.

"There was an exchange of fire between both sides and the first (wave) has been postponed."

An affiliate group of the Islamic State in Iraq and Syria (ISIS), which holds a small pocket in the southwest of Daraa, is excluded from the ceasefire deal.

The regime bombardment campaign on rebel-held areas in Daraa since June 19 had killed more than 160 civilians, the Observatory says.

Before the deal was announced, the advance by Russia-backed regime forces had doubled their control of territory in the province to more than 60 per cent.

Since Russia intervened on Assad's side in Syria's conflict in 2015, the Damascus regime has notched up a series of victories against rebels and militants in the country.

Regime forces, who secured the capital Damascus earlier this year, now control more than 60 per cent of the country, according to the Observatory.

The deal between rebels and Russia announced for Daraa is the latest in a string of such accords to see Damascus regain control of rebel-held areas.

These often come after blistering military offensives or crippling sieges, which effectively force the rebels into the so-called "reconciliation" deals.

Syria's war has killed 350,000 people and displaced millions of others since it started with the brutal repression of anti-Assad protests in 2011.

Many Syrians have sought refuge from the war in neighbouring countries, including Jordan, which says it has taken in around 1.3 million Syrian refugees.

Amman last month said its frontier, which has been closed since 2016, would remain so to any more Syrians fleeing the conflict.