Mortar shells struck a school east of Damascus on Wednesday, killing at least 11 children, said activists, and the death toll was likely to rise.

It was the most serious violence against Syrian minors since a twin suicide bombing killed at least 25 children near a school in October.

The children of the Haya School in the town of Qaboun were struck by three mortars, said a local activist who uses the name Abu Akram al-Shami. Another local activist, Amar al-Hassan, based near Damascus, also confirmed the incident, as did Rami Abdurrahman of the Britain-based Syrian Observatory For Human Rights.

Abdurrahman said 11 children were confirmed killed, but the number was likely to rise because of the seriousness of many of the children’s wounds.

One woman screamed as she beat her chest in grief and shock. “My son, my son!” she wept, in a video uploaded of the incident.

Another showed at least five boys bloodied and lying lifeless on the ground of what appeared to a medical faculty.

The videos appeared genuine and corresponded to Associated Press reporting of the incident.

The local activist collective, the Qaboun Media Office, said at least 17 children were killed. Conflicting death tolls are common after such incidents.

It was not immediately clear who fired the rockets. Both pro-government forces loyal to President Bashar Assad and rebels opposed to his rule use the weapons.

There has been a truce in Qaboun for about the past five months between rebels and forces loyal to President Bashar Assad, and the town has not experienced any serious violence since then. The town hosts thousands of Syrians who have been forcibly displaced from other rebel-held areas.

Activists said they believed Assad loyalist forces fired the mortar shells – if only because it was unlikely that rebels would fire at their own people. Government officials had no immediate comment.

Syrian children have often been the victims of the country’s war, now in its fourth year, but they are rarely specifically targeted.

But in October, two suicide bombers targeted a school in the central city of Homs, killing 32 people, including 25 children.

Also in Syria, in the Kurdish-dominated far north and northeastern regions, the Britain-based Syrian Observatory said Kurdish forces were distributing leaflets to residents, ordering them to report to security offices to undertake compulsory military service. Syrian Kurds run their self-declared largely autonomous area, called Rojava.

They have been at the frontlines of fighting the expansion of rebels of the Islamic State group.

Their battle against the rebels in the Syrian border town of Kobani has captured international attention, and the U.S. has assisted the fighters with airstrikes.

Senior Syrian Kurdish official, Anwar Muslim said the move was necessary to repel the rebels.

“We want all of the people to come, train and learn to carry weapons, without discriminating between men and women. We need all people to learn how to carry weapons in order to be able to defend themselves and protect their areas and their villages,” Muslim said. He spoke in Irbil, the capital of the largely autonomous Kurdish area of northern Iraq. SAPA