By Suleiman Al-Khalidi and Angus McDowall
AMMAN/BEIRUT (Reuters) - The Syrian army seized more towns in the southwest on Saturday, as air strikes pounded others that still held out against the rapid offensive and rebels said they had begun negotiating peace terms through the government's ally Russia.
State television broadcast from the town of Dael, northwest of Deraa city, after the army entered, and a war monitor reported that several towns further east had also accepted government rule.
Rebels expected to hold another meeting on Saturday with Russian officers to negotiate a deal for the return of Syrian state sovereignty over the whole of Deraa province, an insurgent spokesman said.
Air raids continued in the meantime, said the Syrian Observatory for Human Rights, in an offensive that the United Nations says has driven 160,000 people from their homes, threatening a humanitarian catastrophe.
Russia, the Syrian government's strongest supporter, has backed army advances with air strikes since entering the war in 2015 and has played a role in mediating surrender deals.
Southwestern Syria is one of two remaining rebel strongholds, along with a region of the northwest that Syrian President Bashar al-Assad has sworn to recapture. He also wants to take back control of territory in northeastern Syria held by U.S.-backed Kurdish forces.
The army's offensive follows the capitulation of rebel enclaves near Homs and Damascus, including eastern Ghouta, which was recaptured after a scorched-earth assault that killed over a thousand civilians and laid waste to several towns.
Warfare in the southwest could risk a further escalation because of its proximity to Israel. The Israelis have already targeted Iran-backed militia fighting on Assad's side, which they have vowed to keep far from their country's borders.
The government's offensive so far has focussed on Deraa province, which borders Jordan, but not Quneitra province abutting the Israeli-occupied Golan Heights. The deal being discussed does not include Quneitra, the rebels said.
The entire southwest is part of a "de-escalation zone" agreed last year by Russia, the United States and Jordan. Despite Washington's threats that it would respond to breaches of that arrangement, it has shown no sign of doing so, and the opposition's top negotiator on Thursday accused it of having struck a "malicious deal" to stay silent.
Insurgent negotiators and a spokesman said a six-member civilian and military committee of the southern rebels held a preliminary meeting along the administrative borders of neighbouring Sweida province.
"The committee held its first meeting with Russian officers who presented their demands," said Ibrahim Jabawi, a spokesman of the central operations room set up by the main Free Syrian Army groups in southern Syria.
But Russian negotiators had still not arrived several hours after another meeting was due to begin on Saturday, Jabawi said.
Jordan has been facilitating talks between rebel factions and Moscow over a deal that would end the violence in exchange for the return of state rule in Deraa province on its border.
Russian negotiators have demanded rebels accept terms like those agreed for eastern Ghouta, where insurgents either left for opposition territory in the northwest along with their families or accepted the return of state rule, Jabawi said.
The southwest rebels did not accept this, and were instead proposing the return of civilian state institutions in the opposition areas and the entry of Russian military police rather than Syrian government forces.
The army has already captured large parts of the eastern zone of rebel-held territory in Deraa province in less than two weeks of fighting, however, and several more towns still held by the insurgents have reportedly agreed to settle with Assad.
On Saturday, state television said the town of al-Ghariya al-Sharqiya had accepted a "reconciliation" agreement with the government, and the national flag had been raised there.
It broadcast live from the town of Dael, where a crowd was shown chanting slogans in support of Assad and the army.
State TV said on Friday that four nearby towns had agreed to surrender their arms and accept state rule. The army had gained control over the towns of al-Harak, Ibta and Rakham, it said, and a rebel said opposition lines in one area had collapsed.
The Observatory said Russian military police had entered several other towns and villages in deals to end their rebellion against Assad.
It reported that warplanes carried out 32 air strikes overnight as the offensive continued, hitting nine towns in Deraa province. So far, about 100 civilians have been killed in air raids and shelling since June 19, it said.
Clashes escalated around Deraa city, which lies close to the border with Jordan, and where army advances could cut the insurgent territory in the southwest in two, it said.
(Reporting by Suleiman Al-Khalidi, Editing by Larry King and Catherine Evans)