The bombings in the town of Reyhanli, just a few kilometres from the main border crossing into Syria, come amid increasingly bellicose criticism by Ankara of the regime in Damascus.
Interior Minister Muammer Guler said the explosions were caused by car bombs that blew up near the town hall and the post office in Reyhanli, according to the Anatolia news agency.
Guler told NTV television that the death toll had climbed to 40 and that 100 people were wounded, updating an earlier toll given by Prime Minister Recep Tayyip Erdogan.
Over a dozen ambulances and several air ambulances rushed to the scene to tend to the victims, Turkish NTV television said, adding that the town hall had suffered major damage.
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A number of cars were also completely wrecked in the attacks whose force caused a power cut in the area around Reyhanli, local media reported.
Guler said the regional governor had been sent to Reyhanli "to put the necessary security measures in place" following the attack.
Thousands of refugees who fled the Syrian crisis are living in Reyhanli and a refugee camp adjacent to the town.
Reyhanli lies in southern Turkey near the Cilvegozu crossing opposite Syria's rebel-controlled Bab al-Hawa border post, the busiest crossing between the two countries.
The border area has witnessed a number of deadly attacks as the conflict in Syria spills over into Turkey, whose government was once an ally of President Bashar al-Assad but has become one of its harshest critics.