Expressing his strong disapproval of the worsening situation in the besieged Eastern Ghouta region, the head of Syria's opposition delegation said Monday that helping civilians must be a priority.

"The situation in Eastern Ghouta is causing serious concern, and the last three months were the worst ever for this region," Nasr al-Hariri, head of the opposition's High Negotiations Committee (HNC), said during a meeting with Russian Foreign Minister Sergey Lavrov on his first-ever visit to Moscow.

"We call on everyone to make the lives of civilians [a top priority] — in Eastern Ghouta, in Idlib, in Raqqah, in Afrin. Saving the lives of the civilians must be a priority for everyone despite the things we have to do in combating terrorism."

Hariri said despite the implementation of safe zones in Syria, there are many regions where the armistice does not work.

Commenting on whether the opposition delegation will take part in the Syrian National Dialogue Congress (SNDC) in Russia's Black Sea resort city of Sochi, Hariri claimed that no final decision has been made.

"We will not make a final decision on our participation in the Syrian National Dialogue Congress in Sochi until we have the exact information about its purpose, which we have to discuss with our international partners and the U.N."

He added that the bombardment of opposition forces in Syria has resulted in their refusal to participate in the SNDC.

Home to some 400,000 residents, Eastern Ghouta has been under siege for five years, and humanitarian access to the city has been completely cut off. Hundreds are in urgent need of medical care.

In the past eight months, the Bashar Assad regime has intensified its siege on Eastern Ghouta, making it almost impossible to bring food or medicine into the district and leaving hundreds of medical patients in need of treatment.

Notably, the district falls within a network of de-escalation zones endorsed by Turkey, Russia and Iran in which acts of aggression are expressly forbidden.

Operation launched on regime-held Turkmen Mountain

Meanwhile, Syria's armed opposition launched an operation Monday on Syrian regime-controlled regions around Turkmen Mountain in Latakia, its commander said. Speaking to Anadolu Agency, Katibat Jabal al-Islam Commander Zahir Abu Usama said Russia is "intensely attacking Idlib." "In order to alleviate these attacks, we have launched an operation around Turkmen Mountain in regime-controlled Sarraf and the surrounding region," he said. Usama said they had seized the villages of Villa and Kapikaya in Sarraf from the regime. It was also reported that many regime soldiers were killed in the opposition's attacks. According to information from local sources, Russian and regime warplanes attacked Turkmen Mountain after the opposition's operation.