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Staffan de Mistura and Sergei Shoigu gathered to "discuss ways of moving from de-escalation zones towards a more stable political settlement in Syria," de Mistura was quoted as saying by a defence ministry statement.

Russia, a key backer of Syrian President Bashar al-Assad, has played a major role in the war and in diplomatic efforts to create and monitor four safe zones across the battle-scarred country. 

Russia agreed during talks in Astana with Iran and Turkey - who back opposing sides in the conflict - to create the zones in the northern Idlib province, in central Homs, the Damascus suburb of East Ghouta and in southern Syria. 

The de-escalation agreement excludes both the Islamic State group and Hayat Tahrir al-Sham, the alliance dominated by al-Qaeda's former Syrian affiliate.

Violence has drastically decreased in the zones since their establishment this year, but conflict is still raging elsewhere in Syria, including a US-led aerial and ground assault on jihadists groups in the country's northeast.

Last month, the UN envoy said he hopes to convene a new round of Syria talks in Geneva in the coming weeks. 

He has already hosted several previous rounds of negotiations, with the fate of Assad a key sticking point. 

The Syrian conflict began when the Baath regime, in power since 1963 and led by Assad, responded with military force to peaceful protests demanding democratic reforms during the Arab Spring wave of uprisings, triggering an armed rebellion fueled by mass defections from the Syrian army.

According to independent monitors, hundreds of thousands of civilians have been killed in the war, mostly by the regime and its powerful allies, and millions have been displaced both inside and outside of Syria.

The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.