Two soldiers and two village guards were killed on Wednesday in a rural area in the province of Batman when the military vehicle they were travelling in drove over a mine planted by rebels from the outlawed Kurdistan Workers' Party (PKK), local security sources said.
Village guards are armed Kurdish militia recruited by the government to support the army against the PKK.
The security forces launched an operation to hunt down the attackers, the sources said.
In the nearby province of Diyarbakir, a Kurdish fighter of Syrian nationality was shot dead when soldiers clashed with a group of PKK rebels near the town of Dicle, officials said.
Tensions in the southeast have escalated since last year when the PKK ended a five-year unilateral ceasefire with the government.
The group waged a bloody campaign for Kurdish self-rule in the region between 1984 and 1999. The conflict has claimed some 37,000 lives.
The Turkish army warned earlier this month that an increasing number of PKK rebels were sneaking back into Turkey from neighbouring northern Iraq, where they had retreated after the 1999 truce.