Syrian soldiers on Thursday bombarded a village where rebels and civilians fled to after being routed the previous day from the strategic border town of Qusayr, a watchdog said.
"The army is using missiles to bombard Eastern Bweida," where thousands of civilians and wounded people who escaped from nearby Qusayr have sought refuge, the Syrian Observatory for Human Rights said.
"The humanitarian situation in Eastern Bweida is grim," Observatory director Rami Abdel Rahman told AFP.
"There is very little food and very few medicines and medical equipment. There is no way the village can deal with the influx."
At least 500 injured people had already fled to Eastern Bweida before the start of a devastating regime assault on Qusayr on May 19, said the Observatory, which relies on a network of activists, doctors and lawyers for its reports.
Although some fighters have stayed behind in orchards near Qusayr and Dabaa, another flashpoint nearby, most of those who fled Qusayr are now in Eastern Bweida, which is under army siege and fierce bombardment.
"The International Committee of the Red Cross must pressure the Syrian regime to allow it to evacuate the injured in Eastern Bweida to a safe place," said Abdel Rahman.
Meanwhile, the regime "has called on Qusayr's residents to return home, but there is nothing but ruins. How are they supposed to return?" he asked.
"Qusayr is completely destroyed, and totally deserted."
Qusayr, strategically located just 10 kilometres (six miles) from Syria's border with Lebanon, was once home to more than 25,000 people.
But thousands of residents fled during the blistering 17-day assault by government forces led by fighters from the Lebanese Shiite movement Hezbollah.
"The rebels put up a fierce resistance, but they didn't have the means to fight back," Abdel Rahman said, referring to the rebels' weaponry.
The insurgents had held onto Qusayr for a year before being ousted on Wednesday.
They have been fighting to overthrow President Bashar al-Assad's regime since his forces launched a bloody crackdown on Arab Spring-inspired protests that erupted in March 2011.