"Deadly attacks on schools yesterday and today across Syria in Idlib, Western Aleppo and Douma which have left more than 25 children and several teachers dead are totally unacceptable … There cannot be any justification or impunity for such acts. Those responsible should be brought to justice," Stylianides said in a statement later Thursday.
According to the EU official, the Idlib attack was the deadliest since the beginning of the Syrian war.
"But sadly, this week alone, attacks have hit already five different schools across the country … I urge all parties to the conflict to ensure that the basic principles of humanity are respected and innocent lives are spared from the hostilities. This conflict has already brought enough suffering to the Syrian people."
Since 2011, Syria has been engulfed in a civil war, following the protests that had turned violent, as part of the so-called Arab Spring. During the conflict, hundreds of thousands Syrians have been killed and millions more have been displaced.