The European Mediterranean Seismological Centre said that the aftershock that occurred on Monday in the Turkish region of Hatay was 2 kilometers (1.2 miles) deep.
At 8:04 p.m. (17:04 gmt), the town of Defne was struck by an earthquake that was felt strongly 200 kilometers (300 miles) away in Antakya and Adana.
Several minutes later, a second magnitude 5.8 earthquake with a focal point near the Hatay district of Samandag jolted the area, according to Turkey’s disaster management service.
According to the state-run Anadolu news agency of Turkey, Syria, Jordan, Israel, and Egypt all felt the tremors.
Hatay province is on the Mediterranean Sea and the disaster agency said the sea level could rise by 50cm (20 inches), warning people to stay away from the coast.
Syria’s state news agency, SANA, reported six people were injured in Aleppo from falling debris, while the mayor of Hatay said a number of buildings have collapsed, trapping people inside.
Witnesses said Turkish rescue teams were running around after the latest quakes, checking if people were unharmed.
Magnitude 7.8 and 7.6 earthquakes struck Turkey’s southeast and neighbouring Syria on February 6, killing more than 47,000 people and leaving one million people homeless along with an economic cost expected to run into tens of billions of dollars.
Mehmet Kokum, an assistant professor of geology based in Elazig, Turkey, said there had been more than 5,000 aftershocks since February 6.
“This is quite expected. We know in our experience the aftershocks will last from months to years. But it’s going to decrease day by day,” he told news reporters.
Lutfu Savas, the mayor for Hatay, said a number of buildings collapsed. Savas said those trapped are believed to have either returned to houses or were trying move furniture from damaged homes.
In the Turkish city of Adana, eyewitness Alejandro Malaver said people left homes for the streets, carrying blankets into their cars.
Some media outlets in Syria’s Idlib and Aleppo regions badly affected earlier this month reported some buildings collapsed and electricity and internet services were interrupted in parts of the region.
The news organisations said many people fled their homes and were gathering in open areas.
The Syrian American Medical Society, which runs hospitals in northern Syria, said it treated a number of patients, including several who suffered heart attacks brought on by fear following the temblor.
The Syrian opposition’s Syrian Civil Defence, also known as White Helmets, issued an alert urging residents in the rebel-held northwest to follow guidelines released earlier regarding earthquakes and how to evacuate buildings.
The death toll from the quakes two weeks ago rose to 41,156 in Turkey, the disaster authority said on Monday, and it was expected to climb further.
An estimated 385,000 apartments were destroyed or seriously damaged and many people are still missing from the February 6 disaster.
Turkey’s President Tayyip Erdogan said construction on nearly 200,000 apartments in 11 earthquake-hit provinces of Turkey would begin next month.