Four suspected bomb makers were killed and 15 people wounded when an explosion ripped through a village in Turkey's mainly Kurdish southeast, security sources and the Interior Ministry said.

The blast occurred at about 10:30 p.m. (1930 GMT) in the Sarikamis district, about 25 km (15 miles) from the region's biggest city of Diyarbakir, as Kurdistan Workers Party (PKK) militants loaded explosives onto a truck, according to the Interior Ministry.

Four of the wounded were in critical condition, security sources said. Witnesses reported hearing the loud explosion from miles away.

The blast followed a car bomb attack near a military facility earlier in the day in an Istanbul suburb that wounded seven people, and a car bombing in Diyarbakir on Tuesday that targeted police and killed three people.

Turkey has been hit by a series of bombings this year, including two suicide attacks in tourist areas of Istanbul blamed on Islamic State and two car bombings in the capital Ankara, which killed a total of 66 people and were claimed by a PKK offshoot.