Beachfront ceremonies in Thailand were the first of hundreds due to be held to mark the disaster's grim anniversary in the dozen countries hit by the earthquake-spawned waves last Dec. 26.
The mourning comes as survivors and officials take stock of the massive relief operation and peace processes in Sri Lanka and Indonesia's Aceh province, the two places hardest hit by the tsunami. In both cases, success has been mixed.
At Bang Niang beach in Thailand's Phang Nga province, Western tourists who were caught in the disaster joined locals early Saturday to placed offerings into a brightly colored, bird-shaped boat that was floated into the Andaman Sea as members of the Moken, or sea gypsy, tribe chanted and banged drums.
The Moken believe the ceremony helps ward off evil spirits.
Peter Pruchniewitz, 68, who was swept from his hotel room and lost a friend to the waves a year ago, returned from Zurich, Switzerland, to attend anniversary ceremonies. Asked why, he said simply, "to remember."
At sundown, about 50 Britons gathered for a solemn Christian prayer service at Phuket island's Patong beach, which was damaged by the tsunami but which now throbs again with activity and nightlife.
In hardest-hit Indonesia, workers on Saturday scaled the minarets of the imposing 16th century mosque in the provincial capital of Banda Aceh, replacing missing tiles and slapping on a fresh coat of whitewash in preparation for special services on Monday.
Thousands of survivors have been rehoused in Aceh, but agencies say they are only about 20 percent of the total number needing new homes. The landscape in many places is still one of devastation.
"It's been a tough year, if anything things have gotten worse as things went on," said Nila, a 42-year-old Indonesian woman who lost three children to the waves. "I somehow feel lonelier."
The tsunami brought one positive side effect in Aceh: it resulted in a cease-fire between the government and guerillas to end a decades-old separatist conflict.
No such progress was made in Sri Lanka, where disputes over aid delivery and an upsurge in violence blamed on separatist Tamil Tiger rebels have dashed hopes that the tsunami would bring a final end to the country's long-running civil conflict.
Troops on Saturday patrolled the streets of the capital, Colombo, amid boosted security for tsunami ceremonies.
Exactly one year ago on Monday, the most powerful earthquake in four decades, magnitude 9, ripped apart the ocean floor off Sumatra island, displacing millions of tons of water and sending giant waves crashing into Indian Ocean coastlines from Malaysia to east Africa.
A dozen countries were hit. Entire villages in Indonesia and Sri Lanka were swept away, five star resorts in Thailand were swamped, and in the Maldives whole islets temporarily disappeared.
At least 216,000 people were killed or disappeared in the waves, according to an assessment by The Associated Press of government and credible relief agency figures for each country hit, though the United Nations puts the number at least 223,000.
The true toll probably will never be known. Many bodies were lost at sea, and in some cases the populations of places struck were not accurately recorded.
Almost 400,000 houses were reduced to rubble and more than 2 million people left homeless, the U.N. says.
The world responded with pledges of some $13.6 billion. Rebuilding has started in some places, and fishing boats and seeds have been handed out to kick-start ruined village economies.
But many refugee camps are still full and their residents rely on handouts to survive.
Former U.S. President Bill Clinton, the U.N. special envoy for tsunami recovery, said much work remained to be done and that the international community faced a "critical challenge" in following through on its promises of help.
"One year ago ... millions of ordinary people across the globe rallied to the immediate aid of communities devastated by the tsunami," Clinton said in remarks prepared for the anniversary and published Saturday in the International Herald Tribune.
"Now our collective challenge is to finish the job, to leave behind safer, more peaceful and stronger communities," he said.
The low-lying island nation of Maldives, where the death toll of 82 was small compared to elsewhere but still endured widespread damage, desperately needs another $113 million in aid but its plight was being overshadowed by countries were the death toll was greater, government spokesman Mohamed Hussain Shareef said.