A powerful underwater earthquake  has struck off the the coast of Indonesia's Sumatra island.

The 7.9 magnitude earthquake on Wednesday damaged hundreds of houses, destroyed bridges and started fires in the costal city of Padang, witnesses told local television.

It was not immediately clear if there were any casualties.

"Hundreds of houses have been damaged along the road," the Reuters news agency quoted a witness in Padang as saying.

"There are some fires, bridges are cut and there is extreme panic here maybe because water pipes are broken and there is flooding in the streets."

The Pacific Tsunami Warning Centre issued regional tsunami warning following the earthquake, but the warning was cancelled soon afterwards.

The Indonesian earthquake comes just hours after a series of tsunamis caused death and devastation on the Pacific island nations of American and Western Samoa.

Padang, the capital of Indonesia's West Sumatra province, sits on one of the world's most active fault lines along the "Ring of Fire", where the Indo-Australia plate grinds against the Eurasia plate, creating regular tremors and sometimes earthquakes.

In 2004, a 9.15 magnitude earthquake, with its epicentre roughly 600km northwest of Padang, caused a tsunami that killed 232,000 people in Indonesia's Aceh province, Thailand, Sri Lanka, India, and other countries across the Indian Ocean.