Turkish Prime Minister Recep Tayyip Erdogan described the killing of three security force members in the southern province of Nigde on Thursday as a "nefarious terrorist attack," but he did not say who was responsible.
Paramilitary forces and police officers were staffing a checkpoint when the attackers opened fire from a truck, Turkey's Dogan News Agency (DHA) said. The driver of the truck, which was stolen, was also killed in the exchange of fire.
Speaking at a rally before March 30 local elections in the northwestern town of Sakarya, Erdogan confirmed the attack.
"A nefarious terrorist attack has been carried out against our gendarmerie and police in the Ulukisla district of Nigde," Erdogan said.
Two of the assailants were captured alive, and police were still searching for a third, he added. Five other members of the security forces were wounded, local news agencies said.
Southeastern Turkey has seen similar attacks by Kurdish militants in the past, but the region has been relatively calm since a ceasefire was announced last year as part of a peace process between the government and the Kurdistan Workers Party (PKK). The conflict has killed more than 40,000 people in the last decade.
The aim of the assailants was not immediately clear. A statement from Turkish Deputy Prime Minister Besir Atalay raised the possibility that the attack could have been carried out by Syrians.
"In the information I received, there is a note about Syria. It is very grave. They may be aiming to stir up the election atmosphere," Atalay was quoted as saying by Hurriyet newspaper.
Turkey has seen Syria's three-year-long conflict spill into its borders occasionally, with mortar shells exploding on its soil, causing civilian deaths. Turkey, which shares a 559 mile border with Syria, has been among the fiercest opponents of President Bashar al-Assad and has been housing more than 700,000 Syrian refugees.
About half a million refugees live outside the camps, as increasingly disgruntled local communities complain about a rise in robberies and crime.
Al Jazeera and Reuters