Opposition-held area of city at risk of siege as violence erupts days after halt in peace talks and deployment of Russian artillery

Large-scale fighting has erupted in the Syrian city of Aleppo and the surrounding countryside, upending a fragile truce that was meant to pave the way for peace talks and threatening a siege of the opposition-held part of the city and a humanitarian catastrophe.

Government warplanes on Tuesday killed five civil defence workers in airstrikes on the emergency teams’ facilities, highlighting the growing ferocity of the conflict after the halt of the UN-mediated negotiations.

“The shells are everywhere, there are dead people on the ground, and they’re washing the blood from the streets,” said one resident in the government-controlled part of Aleppo.

The latest fighting comes days after a halt in peace talks in Geneva that were brokered by Washington and Moscow, and the deployment of Russian artillery last week in support of an offensive that Syrian government officials have long pledged to pursue.

Forces loyal to Bashar al-Assad are buoyed by recent battlefield advances, largely the result of massive Russian aerial bombardment of rebels fighting to overthrow the Syrian dictator. But progress in recent weeks has been slow with the partial withdrawal of Russian forces ordered by the Kremlin.

Government forces hope to encircle east Aleppo, which is held by the opposition, and are also fighting in the countryside to cut supply lines in the north from Turkey.

Activists in the city said at least 12 people had died on Tuesday in rebel-held areas, the continuation of an aerial campaign that began on Friday and has killed more than 20. Sixteen people died in retaliatory shelling by the rebels on government-controlled territory and more than 80 were injured, state media said, blaming the attacks on Jabhat al-Nusra, al-Qaida’s wing in Syria.

Brita Haji Hasan, the head of Aleppo city’s opposition council, said 25 people a day have been massacred in the city since the Assad regime and their Russian allies broke the ceasefire just under a week ago. He told the Guardian the city had endured five to six days of bombing and machine-gun strafing.

Seven people were killed when a barrel bomb landed in the popular Alsakhour market on Sunday. Thirty people, including women and children, were killed that day in what appeared to be an intensification of the barrage, Hasan said.

He added that the city was under partial siege with the only road out of Aleppo under constant attack.

“The situation is very bad but we are trying to live on,” Hasan said. “If we are besieged it will be a complete disaster.”

The attacks led civil defence volunteers in opposition-run Aleppo to ask citizens to avoid gathering in crowds and stay away from schools, markets and public squares to avoid airstrikes. Schools in Aleppo were closed.

The civil defence itself was targeted by two airstrikes and a missile launch on Tuesday in Atareb, a town west of Aleppo, killing five emergency responders.

“In all other countries around the world, search and rescue teams are immune from bombing under the Geneva conventions, yet this is not the case in Syria,” said Raed Fares, the head of the White Helmets, the name of the civil defence organisation operating in opposition-held areas in Syria. “In Syria, our volunteers are forced to pick up the body parts of their teammates.”

Humanitarian officials fear the latest Aleppo campaign could lead to a full-blown siege of its eastern neighbourhoods, which already lack fuel, water and electricity, and cause a major humanitarian disaster in a city that is already in ruins after four years of fierce combat.

“In the east people are living in the rubble, burning trash to get a bit of heat or make morning tea. I don’t know how they can cope if the fighting really hits Aleppo harder,” said Pawel Krzysiek, the International Committee of the Red Cross’s spokesman in Syria. “Unimpeded and regular access is what we expected from the truce and that didn’t happen. We will not help people if we go only once there. This is not a solution.”

Humanitarian officials say the regular aid deliveries promised in the ceasefire deal have not materialised, with one-off missions into besieged territory occasionally going through. The UN estimates that hundreds of thousands of people are living under siege in Syria, mostly enforced by the Assad regime and its allies, while other organisations believe the number is over a million.