An air strike killed at least 39 people in a Syrian rebel-held town in the northwest when it struck a court house and an adjacent prison, the Syrian Observatory for Human Rights reported on Saturday.

It was not immediately clear who carried out the air strike on the town of Maarat al-Numan in Idlib province, which is said to have also wounded a large number of people, many of whom were in critical condition.

Figures from the Syrian Human Rights Committee (SHRC), estimate the number of civilians killed by the international coalition in 2015 in Syria was 268.

That is just one per cent of the total number of civilians killed in Syria during that time as a result of conflict, which stands at 20,063 according to the SHRC.

It has also recorded 619 incidents where five or more people have been killed at one time, including just 13 which have been attributed to coalition forces.

A recent report by Amnesty International found at least 200 civilians were killed in Russian airstrikes in Syria in the two months to the end of November. It accused Russia, which began airstrikes in September last year, of using internationally banned cluster munitions and unguided bombs in civilian areas.

Philip Luther, director of the Middle East and North Africa Programme at Amnesty International, said: “Some Russian air strikes appear to have directly attacked civilians or civilian objects by striking residential areas with no evident military target and even medical facilities, resulting in deaths and injuries to civilians. Such attacks may amount to war crimes.”

Russia dismissed the report as “total lies” and denied the use of cluster munitions in Syria.

Monitoring organisations have also raised concerns about casualties caused by the Syrian government’s use of cluster munitions and attacks on civilians using highly explosive barrel bombs.

Human Rights Watch identified 249 attacks where cluster munitions were used by government forces between July 2012 and July 2014.

The organisation has also raised concerns about the Syrian government’s imposition of sieges on its citizens such as the situation in Madaya which has reduced residents to starvation.