There has been no tsunami observed near the epicentre of the earthquake that rocked northern Sumatra region on Monday, the United States National Oceanic and Atmospheric Administration 's Pacific Tsunami [Images] Warning Center said.

A small tsunami, though, was recorded in the Cocos Islands, southwest of Indonesia, according to the centre.

But it warned that the 'earthquake has the potential to generate a widely destructive tsunami' and that evacuations of coasts within a thousand kilometers of the epicenter was necessary.

"There's no threat of a tsunami in the Pacific or East Asia," according to Chris Vaccaro, spokesman for NOAA's National Weather Service.

It was difficult to assess the possibility further west, closer to India, because the PTWC had no buoys in the Indian Ocean, he said.

While most reports said Monday's quake, which occurred at 2138 IST, was of magnitude 8.2 on the Richter scale, the NOAA put the quake at 8.7 on the Richter scale.