The villages of Fuaa and Kafraya represent a tiny pocket of regime-held territory in Syria's northwest Idlib province, which is otherwise nearly entirely controlled by various jihadist and hardline rebels.
"We are alarmed by the renewed escalation of hostilities and hope that the guarantors will redouble their efforts to avoid seeing a scenario like that of East Gutta or Aleppo again, ' the United Nations coordinator stated, because after evacuating the civilians from these two cities to Idlib, 'there is no other location to move them any more", Moumtzis added.
The airstrikes came a day after jihadists from Al-Qaeda's former Syrian affiliate launched an attack on Fuaa and Kafraya, two villages held by the regime but cut off by hardline forces.
Late on Saturday, Hayat Tahrir Al Sham (HTS) and allied fighters shelled Fuaa and Kafraya heavily and clashed with local fighters.
"This is the fiercest attack in around three years", said Abdel Rahman.
The fighting, which was continuing Sunday, had killed six pro-Damascus fighters and at least three Takfiri elements, he added.
Fuaa and Kafraya are the only two places in Syria now designated as besieged by the United Nations.
Around 10,000 people, majority Shiite Muslims, are estimated to live in the two villages.
Rebels overran most of Idlib in 2015, but the mainstream opposition's influence has dwindled as jihadists like HTS have solidified their grip on the province.
The attack on the night of June 7 targeted the village of Zardana in Idlib province and left 44 dead, including six children, according to the Observatory.
The spokesman noted that the Secretary-General recalled that Idlib is part of the de-escalation agreement reached in Astana, and called on its guarantors "to uphold their commitments".
Panos Moumtzis, UN Regional Humanitarian Coordinator for the Syria Crisis, shows a Syria's map to the media during a press conference on humanitarian access in Syria, during a press conference, at the European headquarters of the United Nations in Geneva, Switzerland, Monday, June 11, 2018.
"We worry about 2.5 million people becoming displaced towards Turkey".
Syrian forces later moved to liberate other militant-held areas in the provinces of Homs and Hama.
Moumtzis said that 920,000 people were displaced within Syria between January and April, the highest number of any four-month span since the war began. Its local rivals hold about a third and the regime controls about 10 per cent, according to the Observatory. Russian Federation entered the Syria conflict in September 2015, offering support to Damascus, which changed the course of the war, allowing government troops to retake more than half the country from opposition and Daesh terrorists.