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. It struck at a depth of 10 kilometres, the European Mediterranean Seismological Centre (EMSC) said.
CNN Turk showed a rescue team climbing a ladder to enter one building where some people had been trapped after the latest tremor. It said the quake struck while people were in the already damaged building to retrieve possessions before it was demolished.
Turkish Health Minister Fahrettin Koca said 294 people were injured in Monday evening's earthquake, 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 the country's Disaster and Emergency Management Authority AFAD had reported one person dead on Monday, residents said more buildings collapsed but most of the town had already fled after the initial earthquakes. Mounds of debris and discarded furniture lined the dark, abandoned streets.
US Secretary of State Antony Blinken said on a visit to Turkey on Monday that Washington would help "for as long as it takes" as rescue operations in the wake of the February 6 earthquake and its aftershocks wound down, and the focus turned to toward shelter and reconstruction work.
The death toll from the quakes two weeks ago rose to 41,156 in Turkey, AFAD said on Monday, and it was expected to climb further, with 385,000 apartments known to have been destroyed or seriously damaged and many people still missing.
President Tayyip Erdogan said construction work on nearly 200,000 apartments in 11 earthquake-hit provinces of Turkey would begin next month.
Total US humanitarian assistance to support the earthquake response in Turkey and Syria has reached $US185 million ($A268 million), the US State Department said.
Among the survivors of the earthquakes are about 356,000 pregnant women who urgently need access to health services, the United Nations sexual and reproductive health agency has said.
In Syria, already shattered by more than a decade of civil war, most deaths have been in the northwest, where the UN said 4525 people were killed. The area is controlled by insurgents at war with forces loyal to President Bashar al-Assad, complicating aid efforts.
Syrian officials said 1414 people were killed in areas under the control of Assad's government.
Medical charity Medecins Sans Frontieres (MSF) said a convoy of 14 of its trucks had entered northwestern Syria from Turkey on Sunday to assist in rescue operations.
The World Food Program has also been pressuring authorities in that region to stop blocking access for aid from Syrian government-controlled areas.
Thousands of Syrian refugees in Turkey have returned to their homes in northwest Syria to get in touch with relatives affected by the devastation.
At the Turkish Cilvegozu border crossing, hundreds of Syrians lined up starting early on Monday to cross.
