The fighting errupted Thursday in a mountainous area in Bingol province after the army launched an operation against the separatist Kurdistan Workers Party (PKK) to thwart the group's "winter positioning" preparations, the sources, who spoke on condition of anonymity, said.

One soldier was injured.

The Bingol governor's office had reported fighting in the region Thursday evening, but said there were no casualties.

The PKK, blacklisted as a terrorist group by Ankara and much of the international community, called a unilateral ceasefire on October 1 in what it described as an effort for a peaceful resolution of the Kurdish conflict.

But the truce, like previous ones called by the group, was rejected by Turkey. Fighting has markedly decreased since then.

More than 37,000 people have been killed since the PKK took up arms for self-rule in Turkey's mainly Kurdish southeast.