Mourners gathered at a memorial ceremony in Ban Nam Khem on Thursday, a small fishing village in Phang Nga province in Thailand. (AP Video shot by Tian Macleod Ji)

Christmas in 2004, a 9.1 magnitude earthquake triggered tsunami waves that killed some 230,000 people across a dozen countries.

Some 1.7 million people were displaced, mostly in the four worst-affected countries: Indonesia, Sri Lanka, India and Thailand.

One of the deadliest natural disasters in modern history, the 2004 Indian Ocean tsunami marks its 20th anniversary on Dec. 26

Survivors and families of victims visited mass graves, lit candles and comforted one another across Southeast and South Asia in ceremonies to mark the disaster that killed some 230,000 people.

Twenty years after the devastating earthquake and tsunami that claimed over 230,000 lives across the Indian Ocean region, thousands gathered in the capital of Indonesia's Aceh province on Thursday to commemorate the tragedy.