Syrian army mortar and artillery shelling of an area of southern Damascus where Palestinian refugees live has killed at least 20 people, residents and local emergency workers say.

Yarmouk camp and the districts surrounding it have seen the most prolonged fighting in the capital since forces loyal to President Bashar al-Assad launched a counter-offensive to push rebels out of the capital two months ago.

Residents in the camp said that for the last two weeks, Yarmouk had been closed off from neighbouring districts and that they had heard regular clashes. Since early on Thursday they reported heavy bombardment in the area.

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Locals said the army may have intensified its attack on the district in the belief that rebels, who have been sheltering in the nearby neighbourhoods of Tadamon and Hajar al-Aswad, were slipping into Yarmouk, whose Palestinian residents are suspected by authorities of siding with the rebels.

Assad's forces are trying to re-establish full control in Damascus as well as fighting rebels in the northern city of Aleppo.

Anti-Assad stronghold 

Persistent air attacks and bombardment of rebel-held areas in northern and southern provinces in the country have prompted waves of refugees to flee to Turkey and Jordan.

More than 100,000 Syrians left in August alone, the highest monthly total in the past 18 months, the UN refugee agency UNHCR said.

Al Jazeera's Jane Arraf reports on the town recaptured by Syrian forces on the border with Jordan

More than 160,000 Syrian refugees now live in Jordan, and that number is increasing by the thousands every day.

About 8,000 live in a new camp on the border, while the rest are scattered across the country.

In the southern province of Deraa, rebels said 45 army tanks were sent to the border town of Tel Shehab, an anti-Assad stronghold which has served as a transit point for refugees crossing into Jordan.

They said rebels withdrew from the town before the army offensive started. "No shots were fired. There were no clashes," rebel fighter Abu Younis said. Four civilians were killed, a relatively light toll, he said.

"They have burnt homes of several activists but they are only entering homes of known activists and families harbouring the rebels. Over 40 people have been arrested," he said.

Another rebel fighter, who called himself Abu Omar, said the army offensive had been brief.

"The security forces have retreated from the centre of the town but are on its fringe right now and there is a column of tanks on the highway leading to the town," he said.

Al Jazeera is unable to independently verify reports of violence, as the Syrian government has placed strict restrictions on reporting.

Source: Agencies