At least four people, including three soldiers, were killed on Tuesday in a blast that struck a military truck as it traveled along a road in Turkey’s southeastern Tunceli province, according to local officials and state media.

Turkish state TV channel TRT reported the deaths and several injuries on its website, and blamed the attack on terrorists. One of those killed was a passerby.

It was unclear if the attack caused more casualties. Many ambulances were sent to the scene in central Tunceli, the semiofficial Anatolia news agency reported.

An official with the Tunceli governor’s office, who was not identified because he was not authorized to speak to the media, told CNN that the office was not yet able to confirm the number of dead or injured.

There was no immediate claim of responsibility. However, suspicion within Turkey is likely to fall on Kurdish militants.

Tunceli province is a predominantly Kurdish region where frequent clashes have occurred between the Turkish military and fighters from the militant Kurdistan Workers Party, or PKK.

The International Crisis Group said in a report last week that Turkey’s long-simmering war with the Kurdish insurgency had escalated, raising casualties to a level not seen in more than a decade.

More than 700 people have been killed in the past 14 months, according to the conflict resolution organization that has extensively researched Turkey’s war with the PKK.

Turkey, the United States, and the European Union have formally labeled the PKK a terrorist organization.

The Kurds, Turkey’s largest ethnic minority, make up roughly 20 percent of the population.

— CNN’s Yesim Comert contributed to this report.