People have started gathering in prayer and are visiting mass graves in Indonesia’s Aceh province to mark 20 years since the massive Indian Ocean tsunami, one of modern history’s worst natural disasters.

People gathered in prayer and visited mass graves in Indonesia's Aceh province to commemorate 20 years since the Indian Ocean tsunami.

Survivors and victims' relatives will next week mark the 20th anniversary of the 2004 Indian Ocean earthquake and tsunami, which killed more than 220,000 people across more than a dozen countries.At the time of the earthquake,

Thailand marks 20 years since the 2004 Indian Ocean tsunami A 9.1 magnitude earthquake struck off the coast of the Indonesian island of Sumatra on Dec. 26, 2004, triggering a tsunami that killed around 230,