Fourteen representatives of armed opposition groups gathered at the Rixos Hotel for indirect negotiations with delegates representing the Syrian government.
The discussions, which will focus on extending the cease-fire that came into effect on Dec. 30, have been brokered by Turkey, which backs the opposition, and Russia and Iran, who support Bashar al-Assad’s regime.
They will discuss violations of the cease-fire as well as improving security within Syria in a bid to pave the way for a political solution to the six-year conflict.
The UN Special Envoy to Syria, Staffan de Mistura, attended the talks that began at around 1 p.m. local time (0700GMT).
UN-brokered talks between representatives of Bashar al-Assad and civilian opposition figures broke down early last year when Russian support turned the war in Syrian regime’s favor.
Syria’s UN ambassador Bashar al-Jaafari heads the regime side. The Turkish delegation will be chaired by Foreign Ministry Deputy Undersecretary Sedat Onal while Special Envoy Alexander Lavrentiev and Deputy Foreign Minister Mikhail Bogdanov will lead the Russian team.
Iranian Deputy Foreign Minister Hossein Jaberi Ansari and U.S. Ambassador to Kazakhstan George Krol are also participating.
The meeting is due to last until Tuesday evening, the Kazakh Foreign Ministry said. More than 400 journalists will attend.
Groups such as Daesh and Jabhat Fateh al-Sham, formerly known as al-Nusra Front, are excluded from the cease-fire and the talks.
Mohamed Alloush, who heads the Syrian opposition delegation, said the cease-fire needs to be strengthened before a political solution could be reached in Syria.
Speaking to reporters after the first session of talks, Alloush said: "We will not move on to the second step unless a cease-fire is ensured.”
He called for an improvement of the humanitarian situation in besieged areas.
He also insisted that Assad must leave Syria. “A real political solution will actualize when Assad and his supporters leave the country," he added.
Meanwhile, President Nursultan Nazarbayev met de Mistura before the talks, according to a statement from the Kazakh presidency.
“We want negotiations to be successful,” Nazarbayev said.
He said the situation in Syria was a concern for not only the Middle East but for the whole world.
He assured de Mistura the meeting in Astana will make a "significant" contribution to peace talks in Geneva.
De Mistura thanked Nazarbayev for hosting the talks. "Your country sets a great example for the solution of the most difficult problems in the world."
He said Kazakhstan's non-permanent membership to the UN Security Council would provide an additional opportunity for the resolution of the Syrian crisis.
An estimated 400,000 people have been killed and 11 million displaced since the start of the Syrian civil war in March 2011, according to the UN.