By Suleiman Al-Khalidi and Angus McDowall
AMMAN/BEIRUT (Reuters) - A major insurgent-held town in southwestern Syria has accepted the return of President Bashar al-Assad's rule, pro-government media and a war monitor said on Sunday, though some local activists and rebels disputed a deal had been completed.
Losing Bosra al-Sham, a major town near the provincial capital of Deraa, would be a significant loss for the opposition in the teeth of a Russian-backed Syrian army offensive in the southwest that has taken chunks of rebel territory.
Jordan on Sunday mediated a new round of talks between rebels in the southwest and Assad's main ally Russia, seeking a wider truce in the area to avert more bloodshed and another wave of displaced people near its border.
Russia has played a critical role in supporting Assad's two-week offensive with air power and negotiating local deals initially overseen by its military police.
The Syrian Observatory for Human Rights, a state television correspondent and media run by Assad's Lebanese ally Hezbollah said insurgents in Bosra al-Sham, east of the provincial capital Deraa had agreed a deal and were handing over heavy weapons.
Activists distributed footage of armoured vehicles being handed to Russian troops, though some local sources said it was a goodwill gesture as talks went on, rather than a sign that a surrender deal was being implemented.
Diplomatic sources said the wider negotiations were difficult, with Russia insisting on sweeping surrender terms, and rebels seeking an agreement that would make Jordan a guarantor of the safety of Deraa province's 800,000 civilians.
The United Nations said on Friday at least 160,000 people had already fled their homes.
Opposition officials involved in steering the rebel negotiating team said continued air strikes during the talks had undermined trust in the process.
Fighting and bombardment on Sunday initially focused on the area around Tafas, northwest of Deraa, along with heavy air attacks, but later involved clashes in the area between Deraa and Bosra al-Sham, the Observatory said.
Assad's offensive in the southwest aims to reclaim one of two remaining rebel strongholds in Syria, the other being Idlib and adjacent areas in the northwest. Assad's forces captured the last enclaves near Damascus and Homs earlier this year.
Southwest Syria is a "de-escalation zone" of reduced warfare and bombardment agreed by Russia, Jordan and the United States last year. Washington warned it would respond to violations of this agreement, but has done nothing so far. Last week, rebels said the United States had told them not to expect any American military support.
The opposition's chief negotiator in wider U.N. peace talks, Nasr al-Hariri, last week accused the United States of complicity in Assad's southwest offensive, saying American silence could only be explained by "a malicious deal".
A military media unit run by the government's Lebanese ally Hezbollah, a Syrian state television correspondent and the Observatory said rebels in Bosra al-Sham had started to hand over their weapons.
Bosra al-Sham, whose black-rock Roman citadel and theatre are a UNESCO World Heritage site, was captured by rebels in 2015.
Jordan's Foreign Minister Ayman Safadi said the kingdom was engaged in intensive diplomacy with all parties in the conflict to help broker a ceasefire that would ease the plight of displaced civilians.
"We are moving in all directions and with all the parties to bring a ceasefire and protect civilians," he said on Twitter on Saturday.
"The Russian insistence on attempting to impose conditions, their unreadiness to stop the air strikes during negotiations, all this gives us more reason for lack of trust and justified fear," said Adnan Masalmeh, a coordinator of an opposition committee steering the negotiators.
Air strikes have pounded the region since the offensive ramped up two weeks ago, causing at least 160,000 people to flee their homes, according to the United Nations.
On Saturday at least 10 civilians were killed when bombs were dropped on the rebel-held village of Ghasam, relief workers said. The Observatory says more than 100 civilians have been killed since an escalation in fighting on June 19.
Many who fled have sought refuge along the borders with Jordan and the Israeli-occupied Golan Heights. Both Jordan, which already hosts more than half a million Syrian refugees, and Israel, have said their borders will stay shut.
Both countries' militaries have distributed aid supplies to people seeking shelter near the borders.
On Sunday, Israel also said it had deployed more tanks and artillery to the Syrian front as a precaution because of the fighting there. [L8N1TX07Y]
An Israeli army commander told Reuters it was hard to quantify how many people had sought shelter in the area immediately across the border, but that it was in the thousands and there were hundreds more arriving each day.
Southwest Syria was an early hotbed of the uprising against Assad in 2011 that morphed into the seven-year conflict that has cost over half a million lives and pushed half the country's pre-war population from their homes.
(Reporting by Suleiman Al-Khalidi; Additional reporting by Dan Williams in Jerusalem; Writing by Angus McDowall; Editing by Andrew Bolton and Paul Simao)