Several people have been killed in Syria after government and Russian forces bombed the edge of the rebel-held Idlib province, rescue workers and a monitoring group have said.
The bombings followed the failure to agree a ceasefire when the leaders of Iran, Russia and Turkey met in Tehran on Friday.
Iran and Russia have backed a military campaign in the area – which is the rebels’ last remaining major stronghold – despite Turkey’s appeal for a truce.
There were more than 68 air raids in southwestern Idlib and Hama province on Saturday, according to the British-based Syrian Observatory for Human Rights.
The observatory said 19 barrel bombs had been dropped and there was also shelling from government areas.
It described the attacks as the “most intense” since August.
Idlib health chief Munzer Al-Khalil said there was “great fear” in the province that the Syrian regime would ramp up its bombing and attempt to re-capture the area.
“I fear we are about to face the most catastrophic crisis in our war,” he said.
“When they decide to take an area, they first attack hospitals. I am worried this has already started.”
Four deaths were reported in the village of Abdeen after the bombings on Saturday, while another person is said to have been killed in Halba village.
People in Idlib waved flags and banners as they protested against the expected all-out government offensive.
State-run Al-Ikhbariya TV said the government was retaliating against overnight shelling, coming from rebel-held areas, against a government-held town in Hama province, south of Idlib.
Nine people are said to have been killed in Mhradah.
State news agency HAMA said “terrorist” posts had been shelled by government forces in northern Hama.
The rebel-held enclave includes most of Idlib province and Hama province.
Almost half of the more than three million people who live in the area have already been displaced from fighting elsewhere in Syria.
An official in the town of Morek, which serves as a crossing between Hama and Idlib, appealed for Turkey to intervene as it has troops and 12 observations points circling Idlib.
“We need a quick solution or our town will burn,” the official said.
Idlib is the rebels’ only remaining major stronghold and a state-backed attack could be the war’s last decisive battle.
There are an estimated 10,000 fighters, including al Qaeda-linked militants, in the province.