"The situation is worrying and we want to alert local authorities and people so that they can prepare for an evacuation" if a big quake strikes, said Samit Thammasarot, the head of the National Committee on Natural Disaster Warning.

"More quakes could cause a major eruption of underwater volcanos, and that could trigger a tsunami again," he said, urging people living on the Andaman coast to be cautious.

But Samit said the government so far had no plans to issue an evacuation order.

The committee said that between March 9 and 12 it had detected 39 quakes ranging in magnitude from 4.0 to 5.3 near the Andaman Islands, some 500 kilometers (300 miles) west of the southern Thai province of Ranong.

The epicenter of the quakes was located 20 kilometers (12.4 miles) below the seabed, the same depth as the 2004 Indian Ocean earthquake which triggered the killer tsunami that left more than 220,000 people dead in several countries.

In Thailand alone, the tsunami killed some 5,400 people. After the disaster, the government developed an early tsunami warning system in cooperation with neighboring countries and the Pacific Tsunami Warning Center in Hawaii.

"I can assure (people) that we are closely monitoring quakes and will issue warnings if we detect something strong like the tsunami. Our warning system is working well. We have been preparing for that," Samit said.

Related Links
Daily Updates on the World's Natural Disasters