A massive underwater mountain discovered off the Indonesian island of Sumatra could be a volcano with potentially catastrophic power, a scientist said Friday.

Indonesian government marine geologist Yusuf Surachman said the mountain was discovered earlier this month about 330 kilometres (205 miles) west of Bengkulu city during research to map the seabed's seismic faultlines.

The cone-shaped mountain is 4,600 metres (15,100 feet) high, 50 kilometres in diameter at its base and its summit is 1,300 metres below the surface, he said.

"It looks like a volcano because of its conical shape but it might not be. We have to conduct further investigations," he told AFP.

He denied reports that researchers had confirmed the discovery of a new volcano, insisting that at this stage it could only be described as a "seamount" of the sort commonly found around the world.

"Whether it's active or dangerous, who knows?" he added.

The ultra-deep geological survey was conducted with the help of French scientists and international geophysical company CGGVeritas.

The scientists hope to gain a clearer picture of the undersea lithospheric plate boundaries and seafloor displacement in the area, the epicentre of the catastrophic Asian quake and tsunami of 2004.

The tsunami killed more than 220,000 people across Asia, including 168,000 people in Aceh province on the northern tip of Sumatra.

Indonesia is on the so-called Pacific "Ring of Fire," where the meeting of continental plates causes high volcanic and seismic activity.