DIYARBAKIR, Turkey (Reuters) - Five children were hurt on Friday when an explosive ripped through a schoolyard in Turkey’s mainly Kurdish southeast, a region gripped by violence between militants and state security forces for months, security sources said.

The sources blamed the attack on the Kurdistan Workers Party (PKK), saying members tossed a homemade explosive into the yard of the middle school in the Baglar district of Diyarbakir, the region’s biggest city.

There were no immediate claims of responsibility.

Authorities have been battling PKK militants in cities and towns in the southeast since July, after a 2-1/2-year ceasefire collapsed. More than 150 civilians have died in the violence, the worst the southeast has seen in two decades.

Turkey, the United States and the European Union all classify the autonomy-seeking PKK as a terrorist organization.

The attack, which media said may have been a kind of percussive bomb, occurred before the children entered their classrooms to collect their report cards on the last day of the semester, officials said.