Russia has over the years repeatedly struck Syria's last main opposition bastion, but attacks killing civilians had been limited this year until an uptick in violence in late June.

"Russian air strikes this morning" to the west of the city left "three dead from the same family... and six people wounded", the Syrian Observatory for Human Rights said, adding rescue teams were still at work removing rubble.

Four strikes hit the area where rebel bases are also present, added the Observatory, a Britain-based group which relies on a network of sources on the ground in Syria.

With Russian and Iranian support, the government of Syrian President Bashar al-Assad has clawed back much of the territory it had lost to rebels early in the conflict.

The last pockets of armed opposition to the Assad government include swathes of rebel-held Idlib province, controlled by jihadist group Hayat Tahrir al-Sham (HTS), which is headed by the country's former Al-Qaeda affiliate.

Syria's 12-year-long war broke out after the repression of peaceful anti-government demonstrations escalated into a deadly conflict that pulled in foreign powers and global jihadists.

The war has killed more than half a million people and displaced millions.

Since 2020, a ceasefire deal brokered by Damascus ally Moscow and rebel-backer Ankara has largely held in Syria's northwest, despite periodic clashes.

However, in an uptick in violence, Russian air strikes killed at least 13 people in Idlib province on June 25, in what the Observatory said at the time was the deadliest such attack on the country this year.

At least nine civilians, including two children, were among the dead -- six of them killed at a fruit and vegetable market in Jisr al-Shughur.

On June 28, Damascus's defence ministry said Syrian and Russian forces had launched air strikes on rebel bases in the Idlib region.

The operation came "in response to daily and repeated attacks... on civilians" in residential areas in nearby Hama province, the ministry had said.

It did not specify the date of the bombardment, but the announcement came a day after Russian air strikes killed eight HTS-affiliated fighters, according to the Observatory.

The rebel-held Idlib region is home to about three million people, around half of them displaced from other parts of the country.