DIYABAKIR, Turkey (REUTERS) - Four suspected bomb makers were killed and 17 people wounded when an explosion ripped through a village in Turkey's mainly Kurdish south-east, security sources and the Interior Ministry said.

The blast occurred at about 10.30pm (3.30am on Friday, Singapore time) in the Sarikamis district, about 25km from the region's biggest city of Diyarbakir, as Kurdistan Workers Party (PKK) militants loaded explosives onto a small truck, according to the Interior Ministry.

A photograph taken from a police helicopter and provided to reporters by the Interior Ministry showed what appeared to be a massive crater in a field caused by the explosion.

Electricity in Sarikamis had been cut and homes near the blast site suffered damaged, CNN Turk reported.

Two of the wounded were in critical condition, security sources said.

Witnesses reported hearing the explosion as far away as Diyarbakir.

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.

After the blast, security forces set up checkpoints at Sarikamis and searched vehicles entering and leaving the village.

Security sources said the blasts occurred as militants loaded explosives onto the truck that they intended to use in an attack on security forces.