Syrian government forces began an artillery bombardment in Syria's southern province of Daraa on Wednesday, a day after a Russian-brokered truce between rebel fighters and President Bashar Al Assad's government took effect.
The previous day, opposition fighters and civilians began leaving Daraa under the agreement, with the first batch reaching the suburbs of Aleppo in a bus carrying eight people, the UK-based Syrian Observatory for Human Rights said.
The departures were part of a ceasefire deal that also calls on opposition fighters who stay in the province to hand over their weapons, said the observatory.
Mr Al Assad's forces brought in reinforcements – tanks and other military vehicles – to Daraa's western region, the observatory reported. Its report said at least one civilian was shot by regime forces.
At least 38,000 people have been displaced from Deraa in the past month, the UN said on Tuesday.
"This includes almost 15,000 women, over 3,200 men and elderly and over 20,400 children," the UN Office for the Co-ordination of Humanitarian Affairs said.
Deraa was retaken by the government in 2018 but emerged as a new flashpoint as troops tightened control over Daraa Al Balad, a southern district of the provincial capital considered a hub for former rebels.
Clashes including artillery exchanges between the two sides since late July are the biggest challenge yet to the deal that returned Deraa province to government control but allowed rebels to stay in some areas.
Russian-sponsored talks that began after the latest fighting intensified in recent days as the government stepped up its campaign to root out those rebels still in Daraa Al Balad.
Forces linked to the Syrian regime are expected to take up posts in Daraa Al Balad under the agreement, it said.
The pro-government Al Watan newspaper also reported the start of departures, saying that "implementation of the truce agreement has begun".
The UN Office for the Co-ordination of Humanitarian Affairs gave a warning about the critical situation in the volatile district, saying that access to goods and services, including food and power, was "extremely challenging".
The observatory said government forces were restricting the entry of goods into Daraa Al Balad, where it estimates 40,000 people still live.
"They are living under siege with families facing shortages of food, medical services, potable water, power and internet," said the monitor, which relies on a network of sources inside Syria.
UN Special Envoy for Syria Geir Pedersen on Tuesday alerted the Security Council to the pressing need for humanitarian assistance.
"We repeat our calls on all parties to end the violence immediately," he said. "Immediate, safe and unimpeded humanitarian access is needed to all affected areas and communities, including Daraa Al Balad."