Syrian families who returned to their homes in Idlib a week ago when the government announced a ceasefire have been left stranded and under fire after the truce collapsed.
Syria blamed Turkey on Monday for not honouring a plan to halt fighting in the north-western province where three million people, including a million children, face bombardment. The conditional truce lasted three days before President Bashar Al Assad's forces, backed by Russia, said they were resuming military operations.
The office of the UN's senior humanitarian adviser on Syria said in a statement on Thursday that civilians who had gone home were at great risk.
Shelling is also occurring in areas under government control, indicating that Hayat Tahrir Al Sham (HTS) rebels continue to resist the regime's assault, the UN said, urging the fighting to stop.
The Idlib region is supposed to be protected from a massive government offensive by the Turkish-Russian deal, which provided for a buffer zone of up to 20 kilometres between the two sides, free of heavy and medium-sized weaponry.
Last week's brief truce came after UN Secretary General Antonio Guterres announced an inquiry into reports that Syrian and Russia planes had bombed civilian targets including schools and hospitals, breaking international law in an assault that began in late April.
“Aerial and artillery attacks have caused considerable damage to dozens of health facilities, schools, markets, water stations, and other civilian infrastructure,” said the statement on Thursday.
“Parties to the deconfliction system, which was designed to enhance the safety and security of humanitarian personnel and operations, have been formally asked by the UN to provide information regarding incidences that occurred in north-western Syria this year.
“Turkey has replied to some of the requests. We are still waiting to hear from the Russian Federation.”