A siren's wail was followed by a minute of silence Monday as mourners marked the moment a year ago when the Indian Ocean tsunami crashed ashore in Asia, laying waste to coastal communities and sweeping away at least 216,000 lives. From worst-hit Aceh province in Indonesia to the tourist beaches of Thailand and tropical Sri Lanka, thousands of survivors, victims' relatives and officials prepared to hold a minute's silence at the times the waves hit as part of commemoration ceremonies. The tsunami first smashed into Aceh, which was closest to the epicenter of the magnitude 9 earthquake that spawned the 10-meter-high (33-ft.-high) waves. Indonesia's President Susilo Bambang Yudhoyono set off a siren at 8:16 a.m. local time (1:16 a.m. GMT Monday, 8:16 p.m. ET Sunday) to mark the moment followed by one minute of silence. 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 on Sunday before joining a march led by children dressed in white through Nagapattinam, where thousands were washed away. 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. The United Nations puts the number at least 223,000. Margareta Wahlstrom, the U.N.'s assistant secretary-general for humanitarian affairs, urged survivors still waiting for houses and jobs to be patient. "If you don't do things well they will collapse in couple of years," she told The Associated Press 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." Survivors and officials, meanwhile, were taking stock of peace drives in Sri Lanka and Aceh, the two areas hardest hit.