Groups of Indones went to pray in front of mass graves in Sumatra's Aceh province, the Ground Zero of the tragedy, where thousands of victims have been buried, reports Efe news.
Almost all the Indonesian casualties due to the tsunami, caused on this day 15 years ago by a magnitude-9.3 earthquake, were registered in Aceh.
Life has gone back to normal in this tropical province, where many survivors have rebuilt their homes in the same place the originals were swept away by waves of up to 98 feet high.
Following the disaster, countries around the Indian Ocean - such as Thailand, Sri Lanka, India, Yemen and Tanzania - have improved their response capabilities, but the system's maintenance has been poor in the Indonesian archipelago.
In 2008, Indonesia launched an expensive alert system with 22 buoys, but they stopped working four years later due to vandalism and poor maintenance.
Although Indonesia has seismic sensors in place to detect earthquakes and tsunamis, they are less efficient than the buoys.
The shortcomings of the system came to light in September last year, when an earthquake and subsequent tsunami on the island of Sulawesi claimed the lives of 4,300 people.
Consequently, the Agency for Assessment and Application of Technology began installing the first four buoys of a new network that will have 12 devices operational by 2021.
The authorities will also install two underwater fiber-optic cables for real-time transmission of sensor measurements.
The memory of the devastating waves that swept through entire villages remains alive in Indonesia, where one can still visit ships that were dragged up to 4 km inland and have now been converted into museums.
In Banda Aceh, more than 50 people managed to survive on December 26, 2004 by climbing onto one of these boats that was swept in by the water and lodged on top of a house.
A museum and some remnants of preserved ruins also serve to recall the tsunami in the province, which for decades suffered a separatist conflict that was resolved after the tragedy.
After Indonesia, the countries with the most number of victims were Sri Lanka, with more than 35,000 dead, India (16,000), Thailand (8,000), Myanmar (400-600), Somalia (289), the Maldives (108), and Malaysia (75), among others.
( With inputs from IANS )