U.N. Special Envoy to Syria Staffan de Mistura called for the assistance of Russia, Iran and Turkey to reach a cease-fire agreement in Syria. De Mistura made a statement Saturday indicating that the increasing violence in Syria threatens the Geneva peace talks and he urged the three countries to assist in providing the truce.

De Mistura also asked for support for the opposition by sending letters to Moscow, Tehran and Ankara, while indicating the concerns result from the increasing violence in Damascus and Hama regions. He also demanded that these states take immediate measures to establish a cease-fire.

The U.N. Syria envoy also indicated that the escalating violence in the region is threating the ceasefire and would have negative results for Syrian civilians.

The parallel series of talks in Astana, Kazakhstan, aim to bolster the truce to support the U.N. negotiations. Damascus has been the scene of heavy fighting in recent days, with the moderate Syrian opposition making large incursions into east of the Syrian capital, while the Bashar Assad regime has responded with airstrikes on opposition positions.

The last round of Astana talks began on Feb. 23, and ended on March 4 without any clear result. The next meetings in Astana are to be held on May 3-4.

Syria has been locked in a vicious civil war since early 2011 when the Assad regime cracked down on pro-democracy protests, which erupted as part of the "Arab Spring" uprisings with unexpected ferocity. Since then, more than a quarter of a million Syrians have been killed and more than 10 million displaced, according to U.N. estimates.