BEIRUT — A tenuous truce in the Syrian countryside north of Homs was shattered this month when Russian warplanes started to attack the village of Ter Ma'aleh, killing at least a dozen people and sending most of its other residents fleeing.
The assault on the village was part of a wider escalation of violence across the country that has displaced tens of thousands of people in just weeks and led relief workers to warn that Syria is facing one of its most serious humanitarian crises of the civil war.
The intensity of the fighting, they say, is fueling increased desperation as a growing number of Syrians are fleeing to neighboring countries and, especially, to Europe.
The United Nations said at least 120,000 people have been uprooted in Aleppo, Hama, and Idlib provinces this month.
The Syrian National Coalition, the main Western-backed opposition group, said Monday that Russian aerial attacks are now the leading killer of civilians, the Associated Press reported.
Najib Ghadbian, the coalition's UN representative, said Russia's intervention in Syria is facilitating President Bashar Assad's ''war on civilians'' and elimination of moderate opposition forces — contrary to Moscow's contention that its campaign is aimed at countering terrorist extremist groups.
Ghadbian said in a letter to the UN Security Council that Russia has carried out nearly 300 airstrikes since initiating its campaign on Sept. 30.
Most of the displaced Syrians have found shelter near their home villages as they try to wait out the fighting, with few Syrian provinces considered safe and the border with neighboring Turkey closed, for the moment. Others have headed to Greece and northern European countries.
More than 9,000 migrants a day crossed into Greece last week, according to the International Organization for Migration, the most since the beginning of the year.
The influx has overwhelmed authorities in Greece and the northern European countries where most asylum seekers aim to settle. The leaders of those countries moved late Sunday to deal with the increasing flow of tens of thousands of people escaping the war in Syria and elsewhere.
In Homs, Hama, and Aleppo, a Syrian government offensive backed by Russian air power has reactivated dormant front lines and swept through areas that had largely escaped the fighting.
Thousands of families have fled as the government, rebel groups, and the Islamic State all try to hold or capture territory. Aid groups based in Turkey are rushing to provide food and other supplies to civilians, saying they are concerned that roads will be captured or cut by the new hostilities. And with winter approaching, they fear they are running out of time.
"You are really seeing these huge front lines open up, and a significant amount of bombing comes with it," said Sylvain Groulx, the head of mission for Syria for Doctors without Borders. "There is so much displacement. We are very worried."