Iranian soldiers killed in Syria's Aleppo

Iranian forces serving in Syria have suffered what could be their biggest loss since Tehran's Revolutionary Guards intervened in the conflict in support of embattled regime leader Bashar al Assad.

A Revolutionary Guards official told Iran's Fars news agency on Saturday that as many as 13 Iranian military advisors had been killed and 21 wounded in fighting between regime forces and opposition forces the Aleppo governorate.

The fighting broke out on Friday when Jaysh al Fatah, a coalition of armed opposition forces including the Al Qaeda-affiliated Nusra Front, launched an offensive which resulted in the capturing of the strategic village of Khan Touman, located some 15 kilometres southwest of Aleppo.

Social media accounts linked to Jaish al Fatah exhibited the bodies of the Iranian soldiers killed in the village, as well as the bodies of regime-allied Shiite militiamen, also killed in the fighting.

Personal identification documents found on some of the bodies suggest that a number of Afghan citizens trained and deployed in Syria may be among the dead.

Attempts continue to wind down over five years of war in Syria, which has left as many as 400,000 dead according to the UN's envoy the country Staffan de Mistura.

Around half of Syria's population has also been displaced, both internally and externally, triggering the worst refugee crisis since World War Two.

Earlier this week, the United States and Russia brokered a ceasefire in the city of Aleppo itself where agreements over the cessation of hostilities have struggled to hold, particularly in the countryside.

The Syrian Observatory for Human Rights, a British-based group that monitors the conflict, said that Syrian regime and Russian jet planes have intensified their bombing of opposition-held posts in Khan Touman.

Russia's Defence Ministry meanwhile said the "regime of calm" in Aleppo province had been extended "for 72 hours beginning at 1am on Saturday [2200 GMT on Friday]."

The fragile ceasefire in Aleppo first came into force at midnight on Thursday after a wider truce deal in western Syria brokered by Washington and Moscow broke down.

US State Department spokesman John Kirby said also in daily press briefing on Friday that US was committed to keeping the deal in place, as long as possible, and was in touch with Russia to ensure it was holding.

Under the deal, Washington is obliged to pressure opposition forces in Syria to abide by the ceasefire, while Russia instructs its ally, the Assad regime, to do the same.

However, the deal does not include the DAESH terrorist group, the Nusra Front or any other militias designated as terrorist group by the UN Security Council.