In Indonesia at least 4,185 people were killed as the country took the full force of a huge earthquake and tidal waves that swallowed entire coastal villages.
Sri Lanka was hard hit with 4,300 people confirmed dead, and thousands more injured or missing, relief officials and Tamil Tiger rebels said.
At least 2,606 people were killed in southern India, with the chief minister of Tamil Nadu announcing 1,705 deaths in her state alone and at least 300 people killed on the country's Andaman islands.
In southern Thailand at least 392 people were killed, including foreign tourists at famous seaside resorts, and 3,000 injured, officials said.
In Malaysia 42 people, including many elderly and children, were killed, officials said.
A British tourist and 31 other people died in the low-lying Maldives, officials said.
In Bangladesh a father and child were killed after a tourist boat capsized from large waves, local officials said.
The US Geological Survey said the earthquake registered west of the Indonesian island of Sumatra measured 9.0 on the Richter scale.
Death toll:
Indonesia: 4,185
Sri Lanka: 4,300
India: 2,606
Thailand: 392
Malaysia: 42
Maldives: 32
Bangladesh: 2
Total: 11,559