At least 33 people have been killed in airstrikes carried out by the Syrian regime, as new peace talks are due to begin in Russia.

The Syrian Network for Human rights said a mother and her four young children were among those killed in the strikes carried out by the Russian-Syrian military alliance.

Footage of the aftermath of another raid showed bodies strewn among a bombed vegetable market in the town of Sarakeeb in Idlib province.

Doctors Without Borders (MSF) said the Owdai hospital in Sarakeeb was also hit by two of the airstrikes resulting in at least five deaths, including a child, and injuries to at least six people.

The attack occurred while the hospital was receiving injured people from an airstrike that happened an hour earlier.

Meanwhile, the main Syrian opposition negotiating body said it would boycott talks due to begin in the Russian city of Sochi.

They claimed the talks were an attempt to create a separate peace process that would favour Russia's ally Syrian President Bashar al-Assad.

Sara Kayyali, the Human Rights Watch researcher for Syria, said Idlib province had seen a marked rise in the number of injured civilians in the lead-up to the talks.

"In the last 72 hours, we have seen an escalation in strikes on Idlib and in the number of civilian casualties and attacks," Ms Kayyali said.

"This has been going on for weeks now and it's quite concerning that despite a lot of talk about de-escalation zones, the offensive on Idlib has been very concentrated."

Idlib province is the last opposition-held stronghold in Syria but in the last month the Syrian Army and their allies have been advancing into the region.

The UN estimates more than 2 million Syrian civilians are trapped in Idlib between the Turkish border, opposition forces and the advancing Syrian Army.

"This is the tragedy. They don't have many options left," Ms Kayyali said.

"As the strikes are ongoing the Turkish border remains closed to refugees and there's not much really they can do but pray for the best and for the international community to move on this.

"They have set their eyes on Idlib and I don't know what that means for the millions of civilians there."

A teacher who lives in the town of Sarakeb in the rebel-held Idlib province, 30-year-old Abdul Rhaman al-Khaled, said locals in the region were scared for their lives.

"I think [there is] no safe place in Idlib to go. All of Idlib governorate are bombing from warplanes," Mr al-Khaled said.

"My family and my kids are crying. They feel fear. They don't know what to do. They don't know where to go."