The Syrian regime continued to defy American warnings and pounded on Monday the southern city of Daraa, forcing dozens of families to flee an imminent offensive on the region.
The US State Department blamed Russia, a close ally of Syrian regime head Bashar Assad, for the breakdown of a ceasefire agreement reached last year for the region, which borders Jordan and the Israeli-occupied Golan Heights.
Regime forces have been battering rebel-held towns in Daraa province, the cradle of the seven-year uprising, for nearly a week, leaving at least 29 civilians dead, according to the Syrian Observatory for Human Rights.
They then turned to the provincial capital of the same name, launching air strikes and barrel bombs on opposition-held districts early Monday.
More than 55 surface-to-surface missiles slammed into those neighborhoods after midnight, followed by four barrel bombs, the Britain-based Syrian Observatory for Human Rights said.
"It is the first time they drop barrel bombs on Daraa city in more than a year," said monitor chief Rami Abdel Rahman.
The Observatory said the city was struck again around noon, this time with air strikes by Syria's ally Russia.
The attacks prompted dozens of terrified families to stream out of Daraa city.
Many set out in the dead of night to seek shelter in olive groves on the city limits, AFP's correspondent there said.
Washington said it was "concerned" about the situation in southern Syria and was communicating with parties on the ground, including Russia. The US has called on Moscow to adhere to the de-escalation agreement for the region reached last year.
"This is once again an example of Russia flouting arrangements it has entered into with no regard for civilian lives," the State Department added.
The United States appears to have sent conflicting signals on how it might respond to the latest violence. Last month, Washington said it would take "firm and appropriate measures" to protect the ceasefire, but activists in the region say opposition factions groups have since been told not to expect an American intervention to defend them. The State Department's statement did not address the issue.
Opposition factions hold the western half of Daraa city and most of the surrounding province, as well most of the adjacent governorate of Quneitra to the west.
That territory roughly forms a horseshoe, whose bottom curve borders Jordan and includes a military base held by opposition factions since 2014.
The regime meanwhile holds Daraa city's eastern half and nearly all the adjacent province of Sweida.
Front lines had been relatively quiet for nearly a year under the de-escalation deal agreed in July 2017 by Russia, the US and Jordan.
But now, the regime and its Russian allies are pursuing a divide-and-conquer strategy against the opposition factions.
"Capturing the town would allow troops to divide rebel territory to smaller pockets," Abdel Rahman said.
"The civil defense teams have not been able to reach targeted areas because of the intense bombing," the local civil defense center said in an online statement.
The renewed hostilities could put 750,000 lives at risk, the United Nations said.
"Any humanitarian crisis in south Syria must be averted first by sparing civilians the pains of fighting, and second, be responded to swiftly from inside and outside Syria," said Ali al-Zaatari, UN humanitarian coordinator in Syria.
Jordan said on Sunday it could not absorb a new wave of refugees across its border.
On Monday, the UN's Syria envoy Staffan de Mistura met with senior officials from France, Germany, Jordan, Saudi Arabia, Britain and the US.
They expressed "grave concern" at the escalation in southern Syria, de Mistura's office said.
