More than one million people were driven from their homes in Indonesia alone, and rescuers there on Monday combed seaside villages for survivors. The Indian air force used helicopters to rush food and medicine to stricken seashore areas.
Another million were driven from their homes in Sri Lanka where some 25,000 soldiers and 10 air force helicopters were deployed in relief and rescue efforts, authorities said.
At Thailand's beach resorts, packed with Europeans fleeing the winter cold at the peak of the holiday season, families and friends had tearful reunions Monday after a day of fear that their loved ones had been swept away.
Katri Seppanen, 27, of Helsinki, Finland, walked around barefoot, in her salt water-stained T-shirt and skirt, at the Patong Hospital waiting room where she spent the night with her mother and sister. She had a bandaged cut on her leg.
"The water went back, back, back, so far away, and everyone wondered what it was - a full moon or what? Then we saw the wave come, and we ran," said a tearful Seppanen, who was on the popular Patong beach with her family. The wave washed over their heads and separated them.
Fifty-eight half-naked and swimming suit-clad corpses lay in rows outside the Patong Hospital emergency room. Three babies under the age of one were among the victims. A photo of one baby was posted on the wall of victims, the little corpse in a nearby refrigerator.
The earthquake hit at 6:58 a.m.; the tsunami came as much as 2 1/2 hours later, without warning, on a morning of crystal blue skies. Sunbathers and snorkelers, cars and cottages, fishing boats and even a lighthouse were swept away.
Indonesia, Sri Lanka and India each reported thousands dead. Deaths were also reported in Malaysia, Maldives and Bangladesh.
"It's an extraordinary calamity of such colossal proportions that the damage has been unprecedented," said Chief Minister Jayaram Jayalalithaa of India's Tamil Nadu, a southern state which reported 1,705 dead, many of them strewn along beaches, virtual open-air mortuaries.
"It all seems to have happened in the space of 20 minutes. A massive tidal wave of extreme ferocity ... smashed everything in sight to smithereens," she said.
At least three Americans were among the dead - two in Sri Lanka and one in Thailand, according to State Department spokesman Noel Clay. He said a number of other Americans were injured, but he had no details.
"We're working on ways to help. The United States will be very responsive," Clay said.
John Krueger, 34, of Winter Park, Colorado, described being inside his bungalow Sunday on Khao Luk Beach, north of Phuket, with his wife, Romina Canton, 26, of Rosario, Argentina, when the water filled it and blew it apart.
"The water rushed under the bungalow, brought our floor up and raised us to the ceiling. The water blew out our doors, our windows and the back concrete wall. My wife was swept away with the wall, and I had to bust my way through the roof," Krueger said while waiting to talk to a U.S. Embassy official at Phuket City Hall. "It was like being in a washing machine."
Canton was dragged into the ocean for more than an hour until a wave brought her back to land again, with a broken nose and foot scratches all over her body, Krueger said.
The quake was centered 155 miles south-southeast of Banda Aceh, the capital of Indonesia's Aceh province on Sumatra, and six miles under the Indian Ocean's seabed. The temblor leveled dozens of buildings on Sumatra - and was followed Sunday by at least a half-dozen powerful aftershocks, ranging in magnitude from almost 6 to 7.3, and one aftershock Monday that hit India's Andaman and Nicobar Islands.
The waves that followed the first massive jolt were far more lethal.
An Associated Press reporter in Aceh province saw bodies wedged in trees as the waters receded. More bodies littered the beaches. Authorities said at least 4,448 were dead in Indonesia; the full impact of the disaster was not known, as communications were cut to the towns most affected.
The waves barreled across the Bay of Bengal, pummeling Sri Lanka, where more than 4,500 were reported killed - at least 3,000 in areas controlled by the government and about 1,500 in regions controlled by rebels, who listed the death toll on their Web site. There was an unconfirmed report of 500 more deaths on another Web site that provided no details. Some 170 children were feared lost in an orphanage. More than a million people were displaced from wrecked villages.
Devinda R. Subasinghe, the Sri Lanka ambassador to the United States, said the extensive damage will make the rescue effort more difficult. "It's going to take time to figure out access to these areas that have been impacted," Subasinghe said Monday in an interview on CNN. Up to 70 percent of the island's coastline was damaged, he said.
There was sporadic, small-scale looting in the towns of Galle and Matara, and authorities said about 200 inmates escaped from a prison, taking advantage of the chaos after guards panicked and fled when water entered the building.
About 2,300 were reported dead along the southern coasts of India. The private Aaj Tak television channel put the death toll there at up to 3,300, but the report could not be confirmed. At least 431 in Thailand, 48 in Malaysia and 32 in the Maldives, a string of coral islands off the southwestern coast of India. At least two died in Bangladesh - children who drowned as a boat with about 15 tourists capsized in high waves.
In India's Andhra Pradesh state, at least 32 Hindu devotees were drowned when they went into the sea for a religious ceremony to mark the full moon. Among them were 15 children. On Monday, bodies of women and children lay strewn on the sand.
"I was shocked to see innumerable fishing boats flying on the shoulder of the waves, going back and forth into the sea, as if made of paper," said P. Ramanamurthy, 40, of that state.
In Cuddalore, in the worst-hit Tamil Nadu state, survivors huddled Monday in a marriage hall turned makeshift shelter, as fire engine sirens whined outside. Broken boats law on the shore near smashed huts with only frail bamboo frames jutting out of the ground.
The earthquake that caused the tsunami was the largest since a 9.2 temblor hit Prince William Sound in Alaska in 1964, according to geophysicist Julie Martinez of the U.S. Geological Survey.
"All the planet is vibrating" from the quake, said Enzo Boschi, the head of Italy's National Geophysics Institute. Speaking on SKY TG24 TV, Boschi said the quake even disturbed the Earth's rotation.
The quake occurred at a place where several huge geological plates push against each other with massive force. The survey said a 620-mile section along the boundary of the plates shifted, motion that triggered the sudden displacement of a huge volume of water.
Scientists said the death toll might have been reduced if India and Sri Lanka had been part of an international warning system designed to advise coastal communities that a potentially killer wave was approaching. Although Thailand is part of the system, the west coast of its southern peninsula does not have the system's wave sensors mounted on ocean buoys.
As it was, there was no warning. Gemunu Amarasinghe, an AP photographer in Sri Lanka, said he saw young boys rushing to catch fish that had been scattered on the beach by the first wave.
"But soon afterward, the devastating second series of waves came," he said. He climbed onto the roof of his car, but "In a few minutes my jeep was under water. The roof collapsed.
"I joined masses of people in escaping to high land. Some carried their dead and injured loved ones. Some of the dead were eventually placed at roadside, and covered with sarongs. Others walked past dazed, asking if anyone had seen their family members."
Michael Dobbs, a reporter for The Washington Post, was swimming around a tiny island off a Sri Lankan beach at about 9:15 a.m. when his brother called out that something strange was happening with the sea.
Then, within minutes, "the beach and the area behind it had become an inland sea, rushing over the road and pouring into the flimsy houses on the other side. The speed with which it all happened seemed like a scene from the Bible - a natural phenomenon unlike anything I had experienced before," he wrote on the Post's Web site.
Dobbs weathered the wave, but then found himself struggling to keep from being swept away when the floodwaters receded.
The international airport was closed in the Maldives after a tidal wave that left 51 people missing in addition to the 32 dead.
Indonesia, a country of 17,000 islands, is prone to seismic upheaval because of its location on the margins of tectonic plates that make up the so-called the "Ring of Fire" around the Pacific Ocean basin.
The Indonesian quake struck just three days after an 8.1 quake along the ocean floor between Australia and Antarctica caused buildings to shake hundreds of miles away. The earlier temblor caused no serious damage or injury.
Quakes reaching a magnitude 8 are very rare. A quake registering magnitude 8 rocked Japan's northern island of Hokkaido on Sept. 25, 2003, injuring nearly 600 people. An 8.4 magnitude tremor that struck off Peru on June 23, 2001, killed 74.
(Associated Press reporters Gemunu Amarasinghe in Colombo, Sri Lanka, K.N. Arun in Madras, India, and Sutin Wannabovorn in Phuket, Thailand, contributed to this report.)