In Indonesia’s Aceh province a siren sounded at 8.16 am to mark the moment the first wave struck.
The siren is part of a tsunami warning system that did not exist last year.
Aceh is the place that was closest to the earthquake that spawned the tsunami and it bore the brunt of the disaster. Indonesia’s President Susilo Bambang Yudhoyono was joined by thousands of mourners observing a minute’s silence at a ceremony held on a jetty overlooking the sea.
He said it was time to look forward to the future, but it was clear that the the past occupied the thoughts of those who gathered at the site of a single mass grave where more than 45,000 people were buried.