It came as eight civilians were killed in bombardment by the regime and Russia across the northwestern province, the Britain-based Syrian Observatory for Human Rights said.

Idlib and other adjacent territories of Syria held by jihadists have faced intensifying bombardment in the past month.

On Sunday, air strikes hit a hospital in Kafranbel and another located underground on the outskirts of Hass.

The raids were blamed on Russia by the Observatory.

An AFP cameraman filmed the two facilities hit by strikes.

"The hospital in Kafranbel is out of order. The patients were transferred to other facilities in the region," Observatory director Rami Abdel Rahman told AFP, adding one civilian was killed.

In Hass, air strikes blamed on Russia halted services at an underground hospital, said Syria Relief and Development, a non-governmental organisation that runs the facility.

"The hospital... is out of order because of the raids," said Ubaida Dandush, who works for the NGO.

The facility had been evacuated shortly before the bombardments, he said, thanks to alerts from a warning system set up to analyse the flight paths of warplanes.

Footage filmed by the AFP cameraman showed a white cloud rising over farmland where the hospital is located.

The Observatory said the facility had been put "out of service" because of "bombing by Russian aircraft".

It said a third hospital in the north of Hama province had also been hit by Russian strikes, but added that it had not been able to verify the extent of the damage.

The war monitor says it determines whose planes carried out strikes according to type, location, flight patterns and munitions.

On Sunday, the official news agency SANA reported the death of a civilian in a rocket attack by "terrorist groups" on a regime-held town near Idlib province.

A military source cited by SANA accused "terrorist organisations in Idlib of planning attacks" against government areas and army positions.

Idlib is under the administrative control of Hayat Tahrir al-Sham (HTS), which is dominated by a faction previously known as the Al-Nusra Front, before it renounced ties to Al-Qaeda.

Late last month the United Nations condemned attacks in northwestern Syria that damaged a medical centre and put two hospitals out of service.

Russia and rebel-backer Turkey in September inked a buffer zone deal to prevent a massive regime offensive on the Idlib region, near the Turkish border.

But the region of some three million people has come under increasing bombardment since HTS took full control of it in January.

The civil war in Syria has killed more than 370,000 people and displaced millions since it began with the bloody repression of anti-government protests in 2011.