The most powerful earthquake in 40 years triggered massive tidal waves that slammed into coastlines across Asia, killing more than 1,500 people in Sri Lanka, Indonesia, India, Malaysia and Thailand.

Tourists, fishermen, homes and cars were swept away by walls of water unleashed by the 8.9-magnitude earthquake, centred off the west coast of the Indonesian island of Sumatra, where at least 94 people were killed by floods and collapsing buildings, officials said.

But the scope of the disaster became apparent only after waves as high as 20ft crashed into coastal areas throughout the Indian Ocean and Adaman Sea.