The armoured vehicle carrying the soldiers "was hit by a roadside bomb that was hidden" at the edge of a road in Van province, the army said in a statement.
A military official confirmed the attack to AFP, adding that the soldiers had been on their way to the scene of a dozen vehicles set on fire by PKK members when their convoy was hit.
After the bombing, the convoy was hit by several rockets, the official said on condition of anonymity, suggesting the soldiers may have fallen victim to a trap.
Turkey has been waging an offensive against the PKK in the Kurdish-majority southeast following the collapse of a two-year ceasefire in summer 2015.
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Since then, hundreds of members of the Turkish security forces have been killed in attacks, but civilian deaths have rarely been confirmed. Thousands of people have fled the fighting.
President Recep Tayyip Erdogan has vowed no let up in the operation and new Prime Minister Binali Yildirim, unveiling his programme for government on Tuesday, vowed to prioritise the fight against the PKK.
"We will pursue with determination the fight against the separatist terrorist organisation," he said.
The group is regarded as a terrorist organisation by Ankara and its Western allies.