It further said that 30,000 FSA gunmen are in regions under the occupation of the Operation Euphrates Shield and Operation Olive Branch forces, "and a sum 20,000 FSA fighters are to be transferred to Idlib to counter the Damascus forces' upcoming operation".
The U.N. has warned that an assault on Idlib could trigger a humanitarian crisis.
The first attack came in April 2017, when US President Donald Trump ordered US Navy warships in the Mediterranean to fire a total of 59 Tomahawk cruise missiles at a Syrian airbase that the Pentagon had claimed was used to carry put a deadly chemical attack against the people of Khan Shaykhun, in the country's northwestern province of Idlib. "That's something we're monitoring very closely", OCHA spokesman David Swanson told AFP.
Other aid organisations also operate in the area, but their support is mostly limited to providing supplies to civilians already living in the existing border camps.
"They hit with four rockets so we escaped with our flock", he said.
A journalist and resident of the area, Arin Sheikmos, said the government security troops went on an arrest campaign in Kurdish-controlled areas, detaining people it accuses of skipping compulsory military service.
Hundreds of families have fled Idlib's southeastern areas since Saturday, when Russian and regime strikes on the region were the most violent in a month, the Observatory said.
Numerous civilians are there because they fled other parts of war-torn Syria.
Meanwhile, the bombs keep falling.
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Syria's conflict has killed more than 350,000 people and forced millions more out of their homes, but the United Nations has warned a full-blown attack on Idlib could bring unprecedented suffering.
The local council of Morek, a town that serves as a crossing between Hama and Idlib, sent an urgent appeal, asking Turkey for a quick solution.
"Our top line message is there needs to be ways of dealing with this problem that don't turn the next few months in Idlib into the worst humanitarian catastrophe, with the biggest loss of life of the 21st century", Lowcock told reporters in Geneva. There are more than 2 million people in the 70,000 fighters belonging to more than a dozen rebel factions.
Al-Qaeda-linked rebels, known as Hayat Tahrir al-Sham, or HTS, control more than half of Idlib, and much of the Russian and Syrian government rhetoric has focused on a need to defeat the group.
The opposition accuses Russian Federation and its allies of already striking at hospitals and civil defence centres to force rebels to surrender in a repeat of earlier, large-scale military offensives.
The new strategy reflects a push to ramp up pressure on the Syrian regime and its Russian and Iranian backers, as Assad appears poised to complete a remarkable rebound in the country's seven-year civil war.
In Geneva, the United Nations special envoy Staffan de Mistura was negotiating privately with Turkish, Iranian and Russian officials as part of a two-day effort to get the countries to seek political and not military solutions.
Observatory head Rami Abdel Rahman said the raids targeted jihadist and rebel positions, some of which were empty and others in use.
Turkey, fearing an influx of refugees in the event of a major assault, has repeatedly warned against a "massacre" in this last stronghold of the Syrian opposition.
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