The Syrian government’s lead negotiator has denounced what he called his rebel counterpart’s “provocative” comments at the start of peace talks in Astana.
Bashar Jaafari said Mohammed Alloush had acted in a way “removed from diplomacy” at the indirect negotiations convened by Russia, Iran and Turkey.
Mr Alloush accused the Syrian military and its allies of violating a truce.
He also said a political solution to the civil war was the rebels’ preferred choice, but “not the only one”.
The talks in Kazakhstan’s capital are the first at which the opposition delegation is formed exclusively of representatives of armed groups.
UN-brokered negotiations in Geneva involving exiled opposition political figures broke down last April with little progress having been made.
More than 300,000 people have been killed and 11 million others displaced since the uprising against President Bashar al-Assad began in March 2011.