Banda Aceh, Indonesia: Mourners from across the world wept, prayed and observed moments of silence along ravaged Indian Ocean coastlines yesterday to remember those killed by one of nature's deadliest disasters.

A year after the tsunami, a huge recovery operation has brought hope to hundreds of thousands of survivors. But the sorrow, pain and trauma remain strong along with fears that monster waves could come again.

"It was so brutal, so quick, so extensive that we are still struggling to fully comprehend it," UN Secretary General Kofi Annan said in a video message broadcast at the Aceh ceremony. "A year on, there has been tremendous progress in many areas ... And yet in some ways, the most challenging days lie ahead," he said.

In southern Thailand, where some 5,400 Thais and foreign holiday-makers were killed, mourners signed books of remembrance or tossed flowers into the sea.

Memorial plan

Thai Prime Minister Thaksin Shinawatra led his nation in mourning during a beachside ceremony, laying a foundation stone for a tsunami memorial.

Sri Lanka's President Mahinda Rajapakse attended a ceremony that paid tribute to an estimated 31,000 people who perished along the country's coastline.

In India, where more than 10,700 people were killed and 5,600 others are listed as missing, survivors offered tearful tributes.

In Malaysia, hundreds travelled to Penang beaches to pray for the victims. Relatives and friends of the 68 people killed here lit candles and scattered flowers into the sea.

Sweden was preparing to remember its 543 nationals killed with memorials scheduled in Stockholm and two other Swedish cities.