Two rockets were fired at a fishing company's shop in the southern Turkish resort province of Antalya on Friday but did not cause any casualties, Dogan news agency reported.
It said the rockets were fired from a mountainous area at the highway between the city of Antalya and the resort town of Kemer. Ambulances and Special Forces police were sent to the area, it added.
There was no immediate claim of responsibility, but the sources said Kurdistan Workers' Party (PKK) militants were suspected of having planted the bombs.
The bomb which killed the three soldiers was set on a road between the provinces of Diyarbakir and Mardin. The two others were in the provinces of Van and Hakkari and wounded 12 soldiers, two of them critically, the sources said.
Southeastern Turkey has witnessed numerous bombings since the PKK, which has waged a three-decade insurgency for Kurdish autonomy in the region, abandoned a ceasefire in 2015.
The PKK is considered a terrorist group by the United States and European Union, as well as by Turkey. More than 40,000 people, most of them Kurds, have died in the 32-year conflict.