But governments insisted they did not know the true nature of the threat because there was no international system in place to track tidal waves in the Indian Ocean—an area where they are rare—and they can’t afford to buy sophisticated equipment to build one.

Lalith Weeratunga, Sri Lanka’s top relief coordinator, said officials had also failed to learn from floods in June last year that ravaged the country’s south and claimed hundreds of lives.

“We had been very complacent,”Weeratunga said.“People had been predicting earth quakes, tidal waves and we even felt a few tremors recently, but obviously we did not take the warnings seriously.”

“Even after that, we had not learnt a lesson,”said Weeratunga, a senior civil servant who is also the prime minister’s top aide.

The magnitude 9.0 earthquake shifted huge geological plates beneath the sea northwest of Sumatra island, causing a massive and sudden displacement of millions of tons of water.

Indonesian officials said they had no way of knowing that the earthquake had caused the tsunamis, or how dangerous they might have been.

Scientists said seismic networks in the region recorded Sunday’s earthquake, but without wave sensors in oceans that would have tracked the path of the waves, there was just no way to determine the direction a tsunami would travel.

An international warning system in the Pacific was started in 1965, the year after tsunamis associated with a magnitude 9.2 temblor struck Alaska in 1964. It is administered by the U.S-based National Oceanic and Atmospheric Administration.

Member states include all the major Pacific rim nations in North America, Asia and South America, as well as the Pacific islands, Australia and New Zealand.

Tsunamis occur only occasionally, but they are much rarer in the Indian Ocean than the Pacific, where one occurs every few years.