A barrage of Russian strikes on rebel-held towns in southern Syria killed 22 civilians on Thursday, the bloodiest day yet of the government's offensive in the strategic region.
With Moscow's help, Syrian President Bashar al-Assad's army has battered the south for more than a week with air strikes, rocket fire and crude barrel bombs.
The bombardment has forced more than 45,000 to flee their homes in search of safety, according to the United Nations, while others huddle in their basements to wait out the raids.
On Thursday, air strikes identified as Russian killed 22 civilians, a monitoring group said, most of them in a single town.
"At least 35 Russian air strikes hit the town of Al-Mseifra," the Syrian Observatory for Human Rights said.
"One of them hit a basement where people were taking shelter, killing 17 civilians, including five children," the Britain-based monitor said.
The hospital in Al-Mseifra had been put out of service by Russian strikes on Tuesday night, the Observatory and relief organisations said.
The Observatory says it determines who carried out particular strikes based on the type of aircraft and munitions used, the locations and the flight patterns.
Another five civilians were killed in other rebel-controlled areas of Daraa, the main province in southern Syria.
"This is the highest toll since the escalation began on June 19," said Observatory head Rami Abdel Rahman, adding that it brought the overall civilian toll since then to 93.
A doctor in a rural area in the west of Daraa province said his staff was preparing for an influx of critically wounded from Al-Mseifra.
"Because there are no medical services in the eastern countryside and because of the security situation, most of the wounded will be brought to us in the west," said Baha Mahameed, who manages the Union of Medical Care and Relief Organizations (UOSSM)'s operations in the south.
The government offensive has already forced five hospitals to close in the past week, with three closed in the past 48 hours, the Observatory said.
Syria has become infamous for attacks on health workers, with more facilities hit so far this year than in all of 2017.
The rebels hold a horseshoe-shaped band of territory in the south spanning most of Daraa and Quneitra province to west. They also control southern districts of the city of Daraa.
The rest is held by government forces, who also control most of Sweida province to the east.
Despite an internationally brokered ceasefire in place since 2017, the regime began ramping up its bombardment of rebel-held towns in Daraa on June 19.
Russian warplanes began raids on June 23 and on Tuesday the two air forces launched joint bombing operations against rebel-held neighbourhoods of the provincial capital.
At the UN Security Council on Wednesday, Britain, France and the United States condemned Russian involvement in the offensive.
French ambassador Francois Delattre called on "everyone, starting with Russia, to uphold their commitments so that this offensive ceases immediately".
Adopting a divide-and-conquer strategy that has served them well elsewhere in Syria, troops have already lopped off the northeastern arm of the rebel-held horseshoe.
On Thursday, air strikes were focused on the east of Daraa province.
The White Helmets rescue force said dozens of strikes had hit the towns of Busra al-Sham and Herak, forcing waves of people to flee.
The Observatory said the raids were increasingly targeting urban areas.
Rebel-held neighbourhoods of the provincial capital were practically drained of residents.
"All the residents and civilians left. There are no civilians here," said Ahmad Abu Hazem, 26, a rebel fighter inside the city.
Most of the 45,000-plus people who had already fled earlier this week, headed to the sealed border with Jordan.
But Amman has said the border will remain closed. The kingdom already hosts more than 650,000 registered Syrian refugees and estimates the actual number is closer to 1.3 million.
To avoid greater bloodshed, Russia is leading talks involving Syria, Jordan, Israel and the United States, but so far there has been no public progress towards a deal.