Scientists from the Hanoi-based Institute of Geophysics said on Jan. 31 they have found signs that at least three tsunamis have struck the coastal province of Nghe An in ancient times.

The tsunamis were thought to have occurred 4,500-4,300, 4,100-3,900 and 900-600 years ago, according to a two-year study that was recently completed.

Associate Professor Cao Dinh Trieu said scientists found banks of placura placenta-arca granosa shells (a type of mollusc) in Quynh Van, Nghi Tien and Quynh Nghia communes and Dien Chau Town and along the seashore in Nghi Yen that were 4,000-4,600 years old.

Trieu said Vietnam is situated near fault lines where tectonic plates meet in the Pacific, an area that accounts for 80 percent of the world's earthquakes.

Scientists said their findings suggested another tsunami could strike the coast of Vietnam again. Trieu added that an earthquake measuring 9 on the Richter scale along the Manila fault could result in a 7m wave barrelling into the coast of Nghe An Province .

Vietnam has not had any significant studies on the possible occurrence of ancient tsunamis, which Trieu said is critical to understand the country's vulnerability to earthquakes and tsunamis. Since 2005, Vietnamese scientists have been collaborating with experts from Russia on studying Vietnam 's vulnerability to quakes.

The United Nations estimated that in 2009, at least 270,000 people in Vietnam lived in areas potentially affected by tsunamis./.