Astana is hosting a fourth round of talks in the Kazakh capital between the Syrian government and the opposition aimed at resolving the now six-year foreign-backed militancy in the Arab country.

The International Meetings on Syrian Settlement, as the talks are officially known, kicked off on Wednesday and will continue into Thursday.

The talks are moderated by Russia and Iran - as allies of the Syrian government - and Turkey, which sides with the opposition.

The Iranian and Russian delegations have already started the discussions.

On the sidelines of the event, Iranian Deputy Foreign Minister Hossein Jaberi Ansari, who is heading the Iranian delegation, sat down for talks with the United Nations special envoy for Syria, Staffan de Mistura, over the latest developments in Syria.

On the eve of the forum, expert discussions took place between representative of Iran, Russia and Turkey.

At Damascus' request, Iran has been providing military advisory support to the Syrian military in its counterterrorism operations. Russia has been carrying out an aerial campaign in Syria, similarly in coordination with Damascus, since September 2015 to further boost the military’s anti-terror performance.

The three mediators helped bring about a nationwide ceasefire in Syria late last year.

There have been three rounds of negotiations in Astana since January. The talks have been hailed as contributory to a United Nations-brokered process in Geneva.

The Astana discussions have seen participants trying to shore up the ceasefire by agreeing on the establishment of a jointly-run mechanism to monitor the deal, which would report to the UN.

Anuar Jaynakov, a spokesman for the Kazakhstan Foreign Ministry, said the participants include Mohammed Alloush, the chief negotiator of the Saudi-backed High Negotiations Committee, the main opposition group attending the Astana and the Geneva talks.

UN Spokesman Stephane Dujarric told reporters on Monday that the envoy would be in Astana as an observer at the invitation of Kazakhstan's government "in view of the urgency and importance of reestablishing a deescalation of the situation in Syria and moving on confidence-building measures."

Dujarric added that de Mistura would hold talks with the three guarantors and others ahead of the next round of Geneva talks, which diplomats say are expected later this month.