AMMAN (Reuters) - Rebels in the southern Syrian city of Nawa in Deraa province surrendered to the Syrian government on Wednesday after intensive air strikes as the army pressed forward with a Russia-backed offensive in the area.

Nawa, in which at least 100,000 people still live, was the largest urban center left in rebel hands in Deraa province, where the offensive launched last month has defeated rebels across a swathe of territory near Jordan and Israel.

Rebels had agreed to a “reconciliation” deal with the government on Wednesday under which they would give up the hills around the city and surrender heavy weaponry, a statement from Nawa’s negotiation delegation said.

The agreement also stated that Syrian army troops would not enter the city unless they were on their way to fight a nearby Islamic State pocket.

The agreement followed a night of intensive aerial strikes on Nawa from the Syrian army, with reports of dozens of civilian casualties.

A resident said dozens of missiles were also fired on the heavily populated city that lies near Quneitra province adjoining the Israeli-occupied Syrian Golan Heights where the army moved earlier this week to control the remaining parts of the country’s southwest in rebel hands.

“It’s like doomsday,” said Malek al Ghawi in a text message sent to Reuters, adding there were “many corpses in the streets and everyone is unable to pull them.”

“We don’t know where to take the injured, the town has been burnt,” Abu Hashem, another resident said.

The artillery and aerial bombardment came only hours after thousands of displaced people who had taken shelter along the Israeli border returned to the city that the army had nearly completely besieged.

They came back after reports that rebels had reached a surrender deal with the Russian military that would spare the city bombardment, another resident said.

The UK-based Syrian Observatory for Human Rights said a hospital in the city was put out of action as a result of the bombardment, citing what it said were high casualties with “tens of people killed and injured.”

The Syrian opposition accuses Russia and its allies of exacting a harsh punishment on civilians by heavily bombing rebel-held towns, forcing mass displacement of populated areas and causing wide scale destruction.

They say the intensity of the bombardment has forced rebels in many towns to sign surrender deals that offer safe passage to those who want to move to other opposition areas after handing over their weapons, while enlisting those who stay into the military.

Some of the heavy army bombardment came from al-Haara, a strategically located hill captured from rebels on Monday and overlooking the Golan area that is close to Nawa.

The shelling also targeted various rebel-held villages in Quneitra province located only a few kilometers from the Israel border where tens of thousands of people had taken shelter from the offensive.