The blast follows Tuesday's bomb attack in the capital Ankara, the worst in at least a decade which authorities said looked to be the work of the PKK. The Kurdish group denied responsibility for that attack, believed to be a suicide bombing.
Ankara is weighing up a military operation in northern Iraq, where thousands of PKK rebels are based and from where they launch attacks into Turkey.
The head of Turkey's armed forces, General Yasar Buyukanit, has called for a military operation there and Tayyip Erdogan, the prime minister, was quoted as saying late on Wednesday that he agreed with the army.
Earlier, army sources had said the landmine was detonated by remote control, although other security sources said it was triggered by pressure as the vehicle was driven over the mine.
The PKK has been fighting for an ethnic homeland since 1984 and Ankara blames it for more than 30,000 deaths since then.
Tens of thousands of Turkish soldiers are based in Turkey's mainly Kurdish southeast to fight the rebels, who tend to step up attacks in the spring when the weather improves.
On Sunday two forest workers were kidnapped by PKK fighters for cutting down trees in the woods, defying their order. The fighters use the region's rugged terrain to hide from security forces.
Meanwhile, PKK has denied involvement in Tuesday's suicide attack in Ankara.
Turkish officials had noted that the bomber who killed six people and wounded dozens in the capital used methods similar to those of the PKK.
But the PKK denied that it had anything to do with the bombing, the Kurdish news agency Firat reported on its website.
"We openly declare that we have no involvement and do not approve of this kind of act," PKK commanders said in a statement, Firat reported.
The statement accused the Turkish military of trying to win support from the US and Iraqi Kurds for "a cross-border operation that the military has wanted to carry out for a long time".