Diyarbakir, Turkey ? A bomb struck a predominantly Kurdish city in southeastern Turkey on Tuesday, killing seven people and wounding 17, the local governor’s office said.

Authorities said the bomb in the city of Diyarbakir was made from powerful explosives and was set off by a cell phone timer. Although nobody claimed responsibility, the blast occurred in a region where Kurdish separatist rebels are known to be active.

The explosion happened around 9 p.m. and an investigation had begun, according to a statement from the provincial governor’s office, which gave the casualty toll.

The deputy governor of the surrounding Diyarbakir province, Ahmet Aydin, said children were among those killed and two of the injured were in serious condition at a local hospital. Local news stations said five of the seven killed were children.

Diyarbakir is Turkey’s largest Kurdish-majority city, and the blast came as Kurdish rebels fighting for autonomy in the region have stepped up their attacks.