Thousands of civilians have fled regime bombardment on opposition-held areas in Syria's southern province of Deraa since Tuesday, with most moving into other opposition-held areas in the south, according to media reports.
The civilians fleeing al-Herak and Busra al-Harir were "heading to nearby villages under rebel control not affected by the bombardment near the Jordanian border".
The fresh offensive further undermines an international "de-escalation" agreement backed by the United States in the face of a threatened offensive.
Regime planes dropped leaflets this week over opposition-held parts of Deraa province, comparing the area to the Damascus suburbs of Eastern Ghouta and urging its residents to "cooperate" with the armed forces to drive out armed groups.
The regime besieged Eastern Ghouta before waging a crushing military offensive. Regime troops are meanwhile massing, mostly in the nearby Sweida province.
State media said the regime is shelling what it called terrorist posts northeast of Deraa, destroying their weapons.
The regime turned its attention to the south after capturing the last opposition-held areas around the capital, Damascus, earlier this year.
After that string of military victories, the regime has set its sights on retaking rebel-held areas of southern Syria - whether through negotiations or a military operation.
Opposition groups have responded by establishing a joint operations command to coordinate their defence of what the opposition refers to as the "death triangle."
Opposition factions hold parts of the city and areas to its west and east. The rebels also control areas along the borders with Jordan and the Israeli-occupied Golan Heights.
The US, Russia and Jordan negotiated a truce for the area, which borders Jordan and the Israeli-occupied Golan Heights, in July of last year. But the calm has started to unravel in recent weeks.
Israel is believed to be seeking an agreement in which Iran and its allied militias would withdraw from the Israeli-occupied Golan Heights, while the US State Department has said any government assault would "broaden the conflict," and has threatened "firm and appropriate measures in response."
Israel has meanwhile carried out attacks against Syrian and Iranian forces in the area in recent months, after repeatedly warning against any Iranian build-up near the occupied Golan Heights.
Iran is a close ally of al-Assad, and its advisers are embedded with his troops. Iranian-backed armed groups are also believed to be deployed in the area.
Smoke rises after regime forces and their Iranian supporters conduct an operation in Deraa, Syria on June 20, 2018 [Anadolu]