An earthquake of 5.1 on the Richter scale shook the seas some 300 kilometers off Vietnam's central province of Phu Yen early Thursday morning, Vietnam News Agency reported.
Its focal depth reached around 250 kilometers, which made it an "intermediate-depth" quake.
Though the quake was strong, its epicenter was too far from the mainland to cause any damage, the news source quoted the Center for Earthquake Information and Tsunami Warning as saying.
The center also said there was no chance of a tsunami following the quake.
However, the center, which operates under the Institute of Geophysics, is still observing the situation in the East Sea.