Monday's quake, this time with a magnitude of 6.4, was centred near the southern Turkish city of Antakya and was felt in Syria, Egypt and Lebanon.
Turkey's Disaster and Emergency Management Authority (AFAD) said there had been 90 aftershocks. Six thousand tents were sent to the area overnight for residents alarmed by the new quake.
The Hatay provincial governor's building, already damaged in the 6 February quakes, collapsed in the latest tremor, television footage showed.
Turkish Health Minister Fahrettin Koca said 294 people had been injured, with 18 seriously hurt and transported to hospitals in Adana and Dortyol.
Patients were evacuated from some health facilities that had remained in operation after the massive tremors two weeks ago, as cracks had emerged in the buildings, Koca said on Twitter.
In Samandag, where AFAD had reported one person dead on Monday, residents said more buildings had collapsed, but that most of the town had already fled after the initial earthquakes. Mounds of debris and discarded furniture lined the dark, abandoned streets.
Muna Al Omar said she had been in a tent in a park in central Antakya when the ground started heaving again.
"I thought the earth was going to split open under my feet," she said on Monday, crying as she held her 7-year-old son.