Russia's Defense Ministry said on December 26 that its troops had found mass graves in the Syrian city of Aleppo with bodies showing signs of torture and mutilation.

Russian Defense Ministry spokesman Major General Igor Konashenkov said that dozens of bodies have been uncovered, some of them bearing gunshot wounds, according to Russian state news agency TASS.

Konashenkov also accused rebels, who controlled eastern Aleppo before they were pushed out earlier this month, of laying multiple booby traps and mines across town, endangering the civilian population.

Meanwhile Syrian President Bashar al-Assad visited a Christian orphanage near the capital Damascus last Sunday to mark Christmas.

Photographs posted on the Syrian presidency's Facebook page showed Assad along with his wife, Asma, standing with nuns and orphans in the Damascus suburb of Sednaya.

In the northern city of Aleppo, Christians celebrated Christmas for the first time in four years with the country's largest city now under full control of government forces.

The rebel withdrawal from east Aleppo last week marked Assad's biggest victory since Syria's crisis began in 2011.

Christians, one of the largest religious minorities at about 10 per cent of Syria's pre-war 23 million-strong population, have tried to stay on the sidelines of the conflict.  However, the opposition's increasingly outspoken Islamism has kept many leaning toward Assad's government.