The U.S., Iran and Russia have a responsibility in southern Syria's Daraa since they agreed on a de-escalation zone in the area, and they must do something to stop ceasefire violations by the Assad regime, Foreign Minister Mevlüt Çavuşoğlu said Friday.

The strategic southwestern corner of Syria had been under a so-called de-escalation agreement reached between Russia, the United States and Jordan in July last year, but the truce has unraveled in recent weeks.

"The regime has attacked this area. Who had an agreement? The U.S. and Russia. Now they both have a responsibility and they have to stop [the regime's violations]. If all agreements stop working, then the political process, the results of Geneva, Astana and the Sochi summit will lose their importance and meaning," Çavuşoğlu stressed.

The minister urged all countries to respect their obligations in Syria, saying that those who do not will lose others' trust.

For the last 10 days, Daraa has been subject to intense aerial bombardments and ground attacks, with Assad regime forces — backed by Shiite militia groups — capturing the towns of Busra al-Harir and Nahta.

Some 150,000 people were forced to flee as the Assad regime's assault on opposition-held areas in southern Syria showed no signs of stopping.