The bomb, believed to have been activated by remote control, went off late Saturday on a railroad in the province of Mus, derailing a passing freight train and damaging eight of its wagons, the sources said.

The authorities believe the blast was the work of the separatist Kurdistan Workers' Party (PKK), blamed for similar attacks in the past.

Last month, a bomb damaged a freight train in the same province, and in July last year five railway security guards were killed when a bomb ripped through a train in neighboring Bingol.

The PKK, blacklisted as a terrorist group by Turkey, the European Union and the United States, has stepped up its violent campaign this year.

The Kurdish conflict in Turkey has claimed more than 37,000 lives since 1984 when the PKK took up arms for self-rule in the mainly Kurdish southeast.