An "escalation of attacks" in Idlib, Aleppo and Hama governorates in October forced six of the twelve targeted hospitals to close down, while four ambulances were also destroyed, the medical charity MSF said on Thursday. Six of the hospitals were operated by MSF.

MSF did not identify who was responsible for the "significant increase" in airstrikes. Russia has been carrying out an air campaign in support of Syrian President Bashar al-Assad in the same region since the end of September.

Russia has been accused by other medical charities and human rights organizations of killing civilians and targeting hospitals.

Nearly 700 health workers have been killed and 313 attacks carried out on health facilities during five years of conflict in Syria, according to the New York-based Physicians for Human Rights. More than 90 percent of those attacks were committed by Syrian government forces.

"After more than four years of war, I remain flabbergasted at how International Humanitarian Law can be so easily flouted by all parties to this conflict," said Sylvain Groulx, Head of MSF for Syria. "We can only wonder whether this concept is dead."

MSF said the recent airstrikes and fighting have also displaced tens of thousands of people as winter approaches, putting additional stress "on top of the already difficult access to healthcare for these displaced populations."

The airstrikes on hospitals in Syria comes after a US airstrike in Kunduz, Afghanistan earlier this month hit a MSF hospital, killing more than 20. MSF has also accused #link:18809454:Saudi Arabia of targeting to MSF run hospitals this month in Yemen.