Syrian government forces widened their offensive in the country's southwest on Sunday to Quneitra province, a region adjoining the Israeli-occupied Golan Heights, a war monitor and rebel sources said.
Government forces, backed by the Russian military, have captured most of the southwest's Deraa province in the offensive that began in June.
Rebels still hold a strip straddling Deraa and Quneitra provinces which adjoins the occupied Golan Heights. Islamic State-affiliated militants also occupy a pocket on the Jordanian border.
At the same time, a few hundred Syrian rebel fighters and their families were preparing to leave Deraa city, the birthplace of revolt against President Bashar al-Assad, to be taken on buses to opposition-held areas in the north under a surrender deal agreed last week.
The Syrian Observatory for Human Rights and rebels said jets, which they believed to be Russian, bombed an opposition-held village in Quneitra province in the first such aerial strike in around a year.
The Observatory said the forces had seized the village of Mashara, about 11 km (7 miles) from the Golan frontier, after heavy shelling, and were now trying to capture elevated land south of the village with shelling and air strikes.
Lebanese TV station al-Mayadeen, which is close to Damascus, said the Syrian army were advancing towards that elevated Tel Mashara area.
The violence is taking place around 4 km from the line marking the start of the United Nations Disengagement Observer Force zone, an area monitored by a U.N. force since 1974 in the wake of the Arab-Israeli War.
A rebel official in Quneitra denied Syrian forces had taken the village and said fighting continued.
"Over 28 (air) strikes struck Mashara and intense artillery and missile bombardment," Suhaib al-Ruhail said.
Government forces also shelled the rebel-held town of al-Haara in neighbouring Deraa province, the Observatory said.
Deraa city was the scene of the first major peaceful protests against Assad's authoritarian rule in March 2011 which spiralled into a war now estimated to have killed half a million people.
The fighters are leaving the Deraa al-Balad neighbourhood which had been under rebel control for years. Under the deal rebels would hand over weapons, and fighters who do not wish to live under state rule would be transferred out.
A rebel official, Abu Shaima, said at least 500 fighters were going to get on around 15 buses and that his bus was already on the road north to opposition-held Idlib province.
A live broadcast on Facebook from a Syrian state television reporter showed buses on what he said was the outskirts of Deraa city, accompanied by Russian military police and Syrian Arab Red Crescent vehicles.
Abu Bayan, a rebel commander, said most rebels in Deraa have decided to stay put rather than face an uncertain future in the opposition-held north, in the hope Damascus ally Russia keeps to its promises to protect them against any retribution by Syrian authorities.
Fighter Abdullah Masalmah, who had chosen to leave and was about to board the bus, said: "I cannot forget the thousands of those who were killed by the regime let alone the orphans, wounded and the detainees. I don't trust the Russians or the regime."
Syrian state news agency SANA said on Sunday that rebels had been handing over their heavy weapons to the Syrian army, showing images of armoured vehicles and heavy artillery it said had been collected.
A large humanitarian aid operation to government-held areas of southwest Syria began this week, after the U.N. on Monday said the government had asked it to begin deliveries. The offensive had displaced hundreds of thousands of people.
Sixteen trucks carrying 3,000 food parcels reached the towns of Nassib and Um al-Mayathen in Deraa province near a border crossing with Jordan on Sunday, a Syrian Arab Red Crescent (SARC) statement said.
Aid was also delivered to four other areas of Deraa earlier in the week, SARC said.
Sunday's convoy was accompanied by a delegation containing the United Nations humanitarian coordinator in Syria Ali al-Zaatari and representatives of the International Committee of the Red Cross.
"We continue to deliver humanitarian assistance and we will be doubling our efforts on the basis of people's needs. Water, health and education are top needs of the population we are urgently responding to," al-Za'tari said.