BANDA ACEH, Indonesia -- Parents prayed at mass graves Sunday for children swept away by last year's tsunami, and Western tourists returned to palm-fringed beaches to lay wreaths for lost friends. Indian children in white marched through a town where thousands died.

The low-key ceremonies came as the region prepared to formally mark Monday's anniversary of the killer waves that crashed ashore in a dozen countries around the Indian Ocean, leaving at least 216,000 people dead or missing.

"After I come here, I somehow feel satisfied," said Dasniati, a mother who traveled 15 hours to lay petals on a grave that holds the remains of 47,000 victims of the devastation in Indonesia's Aceh province.

Though she has no way of knowing for sure, she thinks her 10-year-old daughter was among those whose bodies were dumped in the pit in the days after the tsunami. "I pray that Allah accepts her at his side," said Dasniati, who like many Indonesians uses only one name.

On Monday, the hardest-hit countries planned official ceremonies and a minute of silence to commemorate the day that a magnitude-9 earthquake ripped apart the ocean floor off Indonesia's coast and sent 30-foot-high waves crashing onto shores.

Flags were to be lowered to half staff in Sri Lanka while bells were to sound in churches, mosques and temples. Hundreds in India were to walk silently to a mass burial ground. In Thailand, thousands of floating lanterns were to be floated to sea.

It was a somber Christmas for many of those who decided to hold private ceremonies Sunday.

Sigi Gsteu, of Feldkirch, Austria, wiped away tears as he told of three close friends who died when the torrents flooded their Thai resort bungalow.

"When a person is missing and you don't have (a body), you cannot say goodbye," he said as he set two simple wooden plaques engraved with his friends' names beneath a lone pine tree where the resort once stood.

At a Christmas Eve service in a hotel on Thailand's Patong beach, the Roman Catholic priest urged worshippers to "remember all those who lost their lives in the tsunami."

Not everyone was thinking of the past, though. Holiday revelers partied with bar staff dressed in Christmas hats in Patong's notorious nightclub district.

After attending Christmas ceremonies on earthquake-shattered Nias island, Indonesian President Susilo Bambang Yudhoyono and his wife, Ani, wept as they hugged children at a home for more than 200 tsunami orphans in the Sumatran city of Medan.

"We promise to rebuild the future for the Acehnese," Yudhoyono said.

In India, more than 300 people attended an interfaith service of Hindu, Christian and Muslim prayers Sunday before joining a march led by children dressed in white through Nagapattinam, where thousands of people were washed away.

At least 216,000 people died or disappeared in the waves, according to an Associated Press assessment of government and credible relief agency figures. The United Nations estimates the number at 223,000.

The tsunami generated one of the most generous outpourings of foreign aid ever known, more money than could be spent in one year. Some $13 billion was pledged to relief and recovery efforts, of which 75 percent has already been secured, the United Nations says.

But the pace of relief and reconstruction has been criticized.

While local economies are recovering, 80 percent of the 1.8 million people displaced by the disaster still live in tents, plywood barracks or the homes of family and friends, according to the aid group Oxfam International.

Margareta Wahlstrom, the U.N. assistant secretary-general for humanitarian affairs, said people have to be patient.

"If you don't do things well they will collapse in a couple of years," she told AP on Sunday. "If you don't take time to do proper planning, and ask people what they want ... then you are going to create new problems along the way."