"We expect the Syrian regime and the sides of Astana (Russia, Turkey and Iran) to immediately fulfill their responsibilities and obligations and to ensure the immediate protection of civilians," EU foreign policy chief Federica Mogherini and humanitarian relief commissioner Christos Stylianides said in a statement.
"Under no circumstances can there be any justification for indiscriminate attacks on women, children and other civilians, their displacement and the destruction of civilian infrastructure," Reuters quoted Federica Mogherini and Stylianides.
"Attacks on civilians and public infrastructure such as schools, markets or hospitals are a reckless and unacceptable escalation," State Department spokesman Morgan Ortigas said on Tuesday.
At the UN Security Council, UN Assistant Secretary-General for Humanitarian Affairs Ursula Mueller confirmed on Tuesday that some 270,000 people had been displaced by violence in Idlib since the end of April. Relief organizations have suspended their work in a number of sectors.
The Syrian Observatory for Human Rights said that the air raids launched by the Syrian regime and artillery shelling on Idlib and its environs led to the deaths of more than fifty civilians, including many children.