BANGKOK: Weaknesses remain in an Indian Ocean tsunami warning system, 10 years after the Boxing Day disaster that killed up to 230,000 people, experts say.

Many buoys used to transmit tsunami warning data have been lost or damaged in recent years, depleting the effectiveness of a $400 million system built across 26 countries, they say.

In Thailand, where massive waves crashed ashore in 2004, killing 5400 people, the only two buoys deployed in the country's exclusive economic zone are not working.

Thailand's National Disaster Warning Centre has confirmed that a satellite channel rental contract for the buoys expired last year and has not been renewed.

Smith Thammasaroj, a former head of the agency who warned in 1998 that south-east Asia could face a deadly tsunami, said giant waves would hit Thailand in less than 30 minutes if a mega-earthquake struck what is known as the Sakraekrang fault line that stretches from the Andaman and Nicobar Islands in the Indian Ocean to southern Thailand and up to Myanmar (Burma).

Mr Smith urged Thailand's military rulers to review the country's disaster warning system that includes towers with loud speakers, despite progress made to alert residents to disasters over the past decade.

''I don't understand why it is not a priority for the agency concerned to fix or replace them with new ones,'' Mr Smith told the Bangkok Post, referring to the buoys. ''We can't avoid another tragedy if we don't have the buoys to warn us in advance,'' he said.

Song Ekmahachai, the agency's acting head, said government funding is being sought to replace the buoys in 2015 as well as building an additional 40 disaster warning towers and improve computer systems. He said his agency's goal is to send out a warning to everyone in the country within two minutes of a possible tsunami being detected.

But Samit Thammasarot, another former head of the agency, told Reuters that if a tsunami happened today Thailand would not be prepared. ''On an official level there has been, in the past, corruption and cut-price equipment bought that does not meet international standards,'' he said.

Seree Suppratid, director of the National Research Centre at Thailand's Rangsit University, said the warnings are too slow and should be brought up to the international standard of not more than 20 minutes. Mr Seree said Thailand should not only rely on international agencies but become an information provider as well.

''If we are to reach that level, the government urgently needs to fix the two buoys which are out of order,'' he said.

The Indian Ocean Warning System is designed to rely on seabed seismic sensors and floating buoys to send alerts to countries within minutes of a quake.

Disaster tsunami-warning centres have been established in Australia, India and Indonesia.

However Reuters reports that all but one of nine Indonesian-operated buoys have been lost or damaged by fishermen and the remaining buoy is not operational. Despite the problems, experts say that since the 2004 disaster warnings have been heard by people living in coastal areas.

In 2012, thousands of people fled Banda Aceh, the city worst-hit by the Boxing Day tsunami, after an 8.6-magnitude quake struck at sea.

Eight years earlier children had run out to collect fish after the sea had retreated, unaware that a gigantic wave was heading towards them that was to kill 167,000 people in Aceh alone.

In Ban Nam Khem, the village worst hit in Thailand in 2004, local leaders run their own evacuation training sessions with around 95 percent of 2000 residents taking part.