Russian ground forces entered the battle with government forces to seize the strategic Humaymat hilltops in northern Hama that fell into rebel hands last week, regaining it after previous successive attempts by the army failed.
"The latest outbreak in violence in Idlib and north Hama has left dozens of casualties, burned several thousand acres of vital crops and farmland and forced at least 300,000 people to flee their homes," WFP spokesman Herve Verhoosel said.
Syrian state media and a military media unit run by Lebanon's Hezbollah group said early on Thursday that the US-led coalition targeted Syrian army positions in Syria's desert, but US military officials denied any knowledge of the strikes.
UNRWA, the UN agency that cares for Palestinians, said on Sunday that conditions in Yarmouk were hellish. "There must be safe passage for the sick and the wounded and the dying civilians," said Chris Gunness, the UNRWA spokesman.