The air strikes on a market in rebel-held Atareb in northern Syria last November 13 killed at least 84 people, including five children, and injured around 150 others, the UN Commission of Inquiry on human rights in Syria said in its latest report.

"The commission confirmed the use of unguided blast weapons by Russian aircraft in a civilian populated area," commission chief Paulo Pinheiro told reporters in Geneva.

He pointed to a "large body of evidence", including interviews with witnesses and forensic analysis of photos, videos and images of weapons remnants, satellite images and impact analysis, to support the commission's findings.

The war crimes investigators acknowledged there was "no evidence to indicate that the ... attack deliberately targeted civilians or the Atareb market."

But they stressed that "The use of unguided bombs, including blast weapons, in a densely civilian populated area may amount to the war crime of launching indiscriminate attacks." 

And Pinheiro pointed out that the use of certain weapons in civilian areas "automatically amounts to (a) war crime ... because of the nature of the weapons used."

The UN's Syria commission, set up in 2011 shortly after the civil war began, has repeatedly accused the various sides of war crimes and in some cases crimes against humanity.

More than 340,000 people have been killed and millions driven from their homes in Syria's seven-year war, with no diplomatic solution in sight.