The quake of magnitude 8.9 on the Richter scale first struck at 7.59am (0059 GMT) off the coast of Aceh province on the northern Indonesian island of Sumatra and appeared to swing north into the Andaman islands in the Indian Ocean.
Close to 2000 people are so far reported to have been killed in southern India where the tidal waves also swept away boats, homes and vehicles, said Home Minister Shivraj Patil.
Patil said the worst affected area was Tamil Nadu state, where 1625 people are reported to have died, followed by Andhra Pradesh state. Kerala state and the Andaman and Nicobar Islands were also hit.
Tamil Nadu's beaches turned into virtual open-air mortuaries as fishermen's bodies washed ashore, and retreating waters left behind others killed inland.
Hundreds of people died in Tamil Nadu's capital Madras and hundreds of others in other districts including Cuddalore, Patil said.
Sea water flooded the streets of Cuddalore town, flipping over dozens of cars and leaving some cars perched atop road dividers.
Residents of Tamil Nadu and Andhra Pradesh state spoke of four-metre walls of water slamming into the shore.
Walls of water
More than 2400 people were killed after the tsunami triggered by the quake struck Sri Lanka, district officials said.
Sri Lanka deployed 20,000 army soldiers in relief and rescue and to assist police to maintain law and order. Military spokesman Brigadier Daya Ratnayake said 2425 people were dead in areas under government control.
Rescue operations are under way
The worst-hit area appeared to be the tourist region of Sri Lanka's south and east.
"The president has declared a state of national disaster due to the seriousness of the situation," President Chandrika
Kumaratunga's office said in a statement.
"President Kumaratunga has appealed to the international
community for emergency assistance," it added.
Indonesian towns nearest the epicentre of the earthquake were levelled by tidal waves that killed at least 1873 people and left bodies wedged in trees as the waters receded, officials said.
Communications were down in several coastal towns, officials said, raising fears that further death and damage were yet to be reported.
Affected residents are fleeing
to higher ground
Aceh province on the northern tip of Sumatra island - which for years has been torn by separatist conflict - was worst hit.
Thousands of people had abandoned their homes and were headed for higher ground after the earthquake, which was centred 40km below the seabed off Sumatra's north coast, sent waves surging inland about 8am (0100 GMT), officials said.
Up to 55 people, many of them children, were killed when a tsunami swept the coast around the Bireuen regency in Aceh province, on the northern tip of Sumatra island, a local mayor said.
An archipelago of 17,000 islands, Indonesia lies along the Pacific Ring of Fire where plate boundaries intersect and volcanoes regularly erupt.
In neighbouring Malaysia, at least eight people were killed after a tsunami struck the popular Batu Ferringhi beach in the northern island of Penang on Sunday, officials said.
Many fishermen were feared missing after the wave hit the western coast of the island, search and rescue officials said.
Several fishermen are missing in
Malaysia's idyllic Penang island
"Many fishing boats had gone out to sea this morning and not all have returned. There are still some out there," Penang Civil Defence Director Mohammed Johari Mohammed Taufik said.
In the idyllic Maldives islands, two-thirds of the capital, Male, was flooded by tsunami waves, the chief government spokesman said.
"The damage is considerable," Ahmad Shahid said. "The island is only about one metre above sea level and a wave of 1.3 metres high swept over us."Resorts struck
At least 257 people were killed and more than 5000 injured in six southern Thai provinces hit by huge tsunami waves, according to officials.
Tourists and locals were being evacuated from several islands, including the tourist island of Koh Phi Phi, Somsak
Those in areas affected by the
tsunamis are being evacuated
Sunwansujarit, deputy director general of the Thai disaster department, said.
Thai Prime Minister Thaksin Shinawatra ordered the evacuation of areas hit by the water.
More than 100 tourists on diving holidays were missing on islands off southern Thailand, about 70 of them in the famed Emeral Cave, a tourist official said.
"We don't know whether they are dead or alive," the official said from the southern city of Trang.
Mizlim Mohammed, assistant director of the Islamic College in Narathiwat, southern Thailand, told Aljazeera: "People near the beaches are being evacuated to high places. Most of the people there are Arab and foreign tourists."
Tremors from the quake were felt as far away as Singapore and Bangkok.