Army chief General Sonthi Boonyaratglin gave the order. He asked officials to focus especially on depots storing old munitions, after an internal report that bombs and ordnance stored at the two dumps were over 30 years old.

"The munitions should have been destroyed long ago. But since Thailand is a poor country, it seems OK to continue storing old US-made munitions, long out of commission by the US Army," Sonthi said.

He said the damage caused by the explosions on Tuesday night was around Bt480,000.

The Army chief apologised to people living near the two dumps for the loud explosions.

Sonthi confirmed the Army's initial assumption that the blasts were caused by excessive heat. He also ordered water to be sprayed on all major munitions dumps in Nakhon Sawan, Ratchaburi and Nakhon Ratchasima as an ad-hoc measure to reduce the temperature in such facilities.

However, Sonthi did not explain why the explosions occurred at 8pm, when the temperature

was much lower than earlier in the day.

Guards on duty saw flames break out at one of the dumps and attempted - unsuccessfully - to put out the fire using extinguishers.

The general said the Army had maintained the high standards for storage of munitions, but the latest explosions in Lop Buri would spur a rethink on more frequent and strict disposal of old ordnance.

In Chiang Mai, five munitions dumps in Fort Kavila, where the 7th Infantry Regiment is based, will be soon relocated to a safer site, further from residential areas - and a fuel storage facility, located just 200 metres across the street.

Maj-General Natthaphat Somboonsri, chief of a local Army precinct command, said water and foam would be sprayed on the five dumps whenever the temperature was higher than 40 C, as ordered by the Army chief.