Fears are mounting about the safety of more than 270,000 civilians who have fled recent fighting in southern Syria, with aid groups and local doctors issuing urgent appeals for people stranded in the desert without shelter.

Fighting in Deraa province, a strategic area that borders both Jordan and Israel, has halted while negotiations for a surrender deal between rebels in the region and the Syrian government’s main backer, Russia, continue. But UN officials say more than 270,000 people have fled their homes in the last two weeks, including 160,000 who have headed towards the Golan Heights and the Israeli border.

More than 200 civilians are believed to have been killed in the fighting in Deraa, which is meant to be a “de-escalation” zone with a ceasefire guaranteed by Russia, Turkey and Iran in place. The latest bout of violence began in mid-June after a year of relative peace, while the regime of Bashar al-Assad pursued military campaigns in other parts of the country.

“The humanitarian situation is bad,” said one doctor in Quneitra, near the Golan Heights, who asked to remain anonymous owing to concerns for his family’s safety. “It’s a small area to which entire towns and villages have been displaced, and it’s a major tragedy.”

Deraa is symbolic to the Syrian opposition. Deraa city was the birthplace of protests in 2011 that spread throughout Syria before evolving into the rebellion against the Assad regime. Most of the opposition fighters in the region are members of moderate rebel groups, part of the Southern Front alliance backed by the US and UK, and managed from a command centre in the Jordanian capital, Amman.

Once one of the most powerful branches of the rebellion, the Southern Front has long been hobbled by the reluctant support of their backers and fractures within their own ranks. Western allies signalled last month they would not intervene militarily to protect their proxies.

The Assad regime and Russia turned their military attention towards Deraa after securing other large swaths of Syria, including Aleppo and eastern Ghouta, following a brutal siege and bombardment. The offensive in Deraa has followed a similar pattern of splitting rebel territory and negotiating “reconciliation deals”, whereby rebels lay down arms and are either forcibly displaced to opposition-held territory north near the Turkish border, or remain under government authority.

Some parts of southern Syria have already surrendered, and a ceasefire has taken hold for two days amid negotiations between rebel groups and the Russians.

Internally displaced people from Deraa arrive near the Israeli-occupied Golan Heights. Photograph: Alaa Faqir/Reuters

Medics say eight hospitals have been bombed since the offensive began on 19 June. Ahmad al-Dbis, an official at the Union of Medical Care and Relief Organisations, which manages hospitals in opposition-controlled parts of Syria, said three of its staff had been killed along with three other medical workers. In total, more than 210 civilians were killed and 500 injured, including rescue workers.

But the massive displacement of civilians has caught many by surprise, exacerbating a humanitarian crisis in a country where half the population has been displaced over the seven years of war.

The offensive on Deraa has been rumoured for months, but was politically sensitive for Israel in particular owing to the possible involvement of Iranian-backed militias and fears that they would establish a presence so close to the border. Israel has said it would not allow refugees to enter the country.

Jordan is also facing mounting pressure to open its border to people fleeing the violence, particularly since local families on both sides of the border share a common heritage and often inter-married before the war. Images and video on social media showed Jordanians flocking to the border with aid supplies for the fleeing Syrians.

But Amman, which sealed the border in 2016 after Islamic State militants killed border guards in a car bombing, has resisted the calls and urged a negotiated ceasefire. More than 600,000 Syrian refugees are already in Jordan.

Amnesty International called on Jordan to open its borders.

“Daraa residents are effectively trapped – many of those who are displaced are living in makeshift tents in the searing heat with insufficient food, water or medical care, and with the constant fear of being exposed to attacks at any given point,” said Lynn Maalouf, Amnesty’s Middle East research director. “Jordan’s border is their only gateway to safety.”

Local doctors say civilians who fled to the border areas are exposed, lacking shelter, tents, sufficient food and water, as well as sanitation. At least 12 children are believed to have died from scorpion bites, dehydration and , drinking contaminated water. Many more are in danger of sunstroke.