Ten of thousands of people have fled to the Turkish border in the past few days as the Syrian army pushed further into the opposition's last major stronghold.
Residents fled from Maarat Al Numan, a main city in Idlib province that has been a sanctuary for families fleeing former rebel areas.
They were escaping a Russian-led campaign that has come close to capturing the town of Khan Sheikhoun further to the south, part of an offensive on the last major rebel stronghold.
"The flow of cars and vehicles leaving is not stopping," said Abdullah Younis, who is from the city.
Residents said about 60,000 people had fled in the past four days.
On Tuesday, Russian and Syrian jets intensified their bombing of scattered villages and towns around Maarat Al Numan, hitting Al Rahma hospital, residents said.
"There were 15 raids on Jarjanaz in less than five minutes," Abdul Rahman Al Halabi told Reuters.
There were no casualty figures from the air strike on Al Rahma hospital in Tel Mannas, said the Syrian Observatory for Human Rights and the Thiqa news agency, an activist collective.
The Observatory said from Britain that the hospital was struck four times but had been evacuated hours earlier.
This month, UN Secretary General Antonio Guterres authorised an investigation into attacks on medical centres and schools in the enclave, after a petition from Security Council members.
Wednesday's air strike was one of several to hit Idlib, home to about 3 million people and the target of government forces for months.
The violence came a day after the main insurgent group in Idlib pulled out of Khan Sheikhoun as the government advanced slowly, clearing land mines and explosives.
The withdrawal of Al Qaeda-linked Hayat Tahrir Al Sham from the town is a blow to the opposition.
Syrian government forces have been on the offensive in Idlib and northern parts of Hama province since April 30, forcing nearly 500,000 people to flee to safer areas further north.
The fighting also killed more than 2,000 people, including hundreds of civilians.
On Wednesday, government forces captured the Teraei Hill, east of Khan Sheikhoun.
Government forces are trying to meet troops marching from the west and lay siege on rebel-held towns and villages in the central province of Hama, the Observatory said.
The army was battling militants but had extended its advance and seized the strategic M5 highway, which runs through the town, linking Aleppo in the north to Homs and Damascus further south.
Activists also reported fighting in the rebel-held areas in the Jabal Al Akrad region in the coastal province of Latakia.
The Syrian Response Co-ordination Group, a relief organisation active in north-western Syria, reported that almost 200,000 people had fled the violence over the past 10 days.
Russian Foreign Minister Sergey Lavrov acknowledged on Tuesday that Russia had ground soldiers in Idlib, the Interfax news agency reported.
Russian military has previously downplayed its direct role in the campaign, where it used mercenaries and special forces and directed battles, western intelligence sources say.