According to the information, Russian warplanes flew attacks on a military camp of the jihadist group HTS on the western outskirts of Idlib. The HTS group, led by the former Syrian arm of the al-Qaeda terrorist network, controls parts of Idlib province, the last bastion of armed opposition to Syria's ruler Bashar al-Assad.

A local AFP correspondent said the attacks took place just after midnight and hit an area outside of Idlib. The area was then cordoned off by the jihadist group.

Russia is Syria's main ally in the civil war that began in 2011 with the crackdown on peaceful protests and turned into a deadly conflict involving other states and international jihadists.

With support from Russia and Iran, Damascus was able to retake much of its territory from rebels. More than a million people were killed in the war and millions were displaced.

Around three million people live in the Idlib region, which is largely controlled by Islamist fighters, around half of them are displaced people from other parts of the country.

The Human Rights Observatory gets its information from a network of local whistleblowers. The information provided by the organization can often hardly be verified by an independent party.