The quake struck at 1344 GMT off the small holiday resort of Ölüdeniz near the Muğla province in the southwest coast of Turkey, said NTV.
Turkey is crossed by several fault lines.
A powerful quake shook eastern Turkey on October 23 last year, killing more than 600 people. It was followed on November 12 by a 5.6-magnitude tremor that killed another 40 people in the same area.
In 1999, two strong quakes in heavily populated and industrialised parts of northwest Turkey killed 20,000 people. (Ankara-Agence France-Presse)