BEIRUT (Reuters) – Government helicopters dropped barrel bombs on Deraa city for the first time in nearly a year on Monday, a rebel and a war monitor said, extending an assault in southwest Syria which has driven thousands from their homes.

Along with the barrels crammed with explosives, the helicopters dropped leaflets saying the army was coming and urging people to “kick out the terrorists as your brothers did in eastern Ghouta”, the sources said.

“My wife and I left with only the clothes on our backs, because the house was completely destroyed,” Muhammad Abu Qasim, 45, told Reuters. Heavy bombing had turned his village northeast of Deraa into “an unbearable hell”.

The region is politically sensitive because of its proximity to Israel and Jordan and because of a “de-escalation” deal there agreed between the United States, Jordan and Syrian government ally Russia.

Washington had warned Syrian President Bashar al-Assad and his Russian allies that violations of the ceasefire would prompt a response, but rebels said the United States had told them not to expect any American military support.

A European diplomat told Reuters the violation of the de-escalation agreement by Russia and Syria was “deeply troubling”.

“No one is in any doubt about the likely military outcome from this uneven clash, but the consequences could be significant. It not only risks a significant humanitarian crisis, but is likely to destabilize further an already precarious situation. It also casts real doubt about Russia’s willingness to stand by its own commitments,” he said.

The fighting has displaced thousands of people and threatens to uproot many more from their homes, adding to the around 6.5 million people already internally displaced by Syria’s seven-year-old conflict.

After fleeing her home many times since the start of war, 30-year-old widow Um Muhammad has once again been forced to move with her three children, and is now sheltering in a school deeper inside rebel territory in southwest Syria.

“Each of us took only our clothes. Right now there’s bombardment everywhere,” she told Reuters.

In Moscow, Deputy Foreign Minister Mikhail Bogdanov was quoted by RIA news agency as saying Russian officials hoped to discuss southwest Syria with U.S. National Security Adviser John Bolton soon, and separately with Jordan.

Jordan’s foreign minister Ayman Safadi said on Twitter on Sunday his country, already hosting hundreds of thousands of refugees, could not take in Syrians fleeing fighting in the southwest and demanded the de-escalation agreement be respected.

BIRTHPLACE OF UPRISING

Assad has turned to the southwest after driving rebels from their last besieged enclaves in western Syria, including eastern Ghouta near Damascus, earlier this year.

It is one of two major areas still held by rebel factions, along with Idlib province on the border with Turkey in the northwest. Deraa, the southwest’s largest city, was an early center of the uprising against Assad in 2011 and has been split into rebel and government sectors for years.

Recent fighting has focused on the town of Busra al-Harir, half way along a narrow rebel salient stretching into government areas northeast of Deraa. If taken, it would split that salient in half, putting the northern part under siege.

The pro-government al-Watan newspaper reported on Monday that the army had advanced into Busra al-Harir.

The UK-based war monitoring group, the Syrian Observatory for Human Rights, reported fierce fighting inside the town between the army, along with allied militia, and insurgents.

But Abu Shaima, spokesman for a central operations room for rebels fighting under the banner of the Free Syrian Army (FSA), said the insurgents had foiled attempts to advance.

Abu Bakr al-Hassan, spokesman for the FSA rebel group Jaish al-Thawra, said Russian planes were carrying out heavy air strikes to support the strong Busra al-Harir offensive.

On Sunday an air strike hit a medical center in Busra al-Harir, causing extensive damage but no casualties, said the Union of Medical Care and Relief Organisations, a charity that works in opposition parts of Syria.

The bombardment has killed about 30 people since it began on June 19, the Observatory reported.

The Syrian military said in a statement on state media on Monday it was committed to protecting civilians in the area.

Russia also said on Monday it had helped the army repel an insurgent attack in the southwest, killing 70 rebel fighters. Syrian state media reported that rebels shelled the nearby city of Sweida.

(Reporting by Angus McDowall and Lisa Barrington in Beirut and Suleiman al-Khalidi in Amman; Additional reporting by Maria Kiselyova in Moscow and Tom Miles in Geneva; Editing by Matthew Mpoke Bigg)