NAGAPPATTINAM, India —  Authorities in southern India (search) warned residents in coastal areas to evacuate Thursday, saying there could be fresh tsunamis (search).

"We have issued an alert. There could be a wave attack in the next one hour," said Veera Shanmuga Mani, the top administrator in Nagappattinam, a coastal town in southern Tamil Nadu state where most of the deaths from the weekend tsunamis occurred.

It was unclear what sparked the warning, but two aftershocks hit islands off of India's eastern coast Thursday morning, the Indian Meteorological Department said earlier.

A moderate earthquake (search), measuring 5.2 on the Richter scale, struck the Greater Nicobar island at 02:43 a.m. Two hours later, another earthquake of the same intensity hit the Little Nicobar island.

Mani said people living within three kilometers (2 miles) from the coastline have been asked to evacuate the area.

Thousands of residents in Nagappattinam began fleeing the town as the warning came in. Police ordered hundreds of vehicles carrying relief supplies and rescue workers not to enter the town.

No other details were immediately available.