The charges of weapons possession without a license are relatively minor, our correspondent said, adding that police hoped to press more serious charges of arms smuggling.

Customs officials who inspected the chartered cargo plane say it contained rocket-propelled grenades, rocket launchers and missile tubes, surface-to-air missile launchers, spare parts and other heavy weapons.

The crew had declared to customs authorities that they were carrying oil drilling equipment.

US tip-off

Thai military and police sources who declined to be named said the US had alerted authorities about the plane's cargo, which flouted UN sanctions against North Korea.

In video


Al Jazeera's Aela Callan reports on
the seized cargo plane

Panitan Wattanayagorn, a government spokesman, said the authorities believed the plane had initially planned to refuel in Sri Lanka and it was not clear why the crew had asked to make an emergency landing in Bangkok to refuel and check a wheel.

"The Thai authorities acted on tips from intelligence agencies of many countries," he said.

Military officials in Colombo meanwhile said the consignment had not been destined for Sri Lanka.

"Why should Sri Lanka buy from North Korea when the same is available in China?" an unnamed official said.

On Saturday a Thai air force official involved in the inspection of the aircraft, who declined to be named, said the US asked authorities to investigate the plane and its cargo.

"We were approached by the United States, seeking our co-operation to examine the suspected plane. It came from North Korea and was heading for somewhere in South Asia, probably Pakistan," the official told Reuters.

Sanctions

Abhisit Vejjajiva, the Thai prime minister, said authorities had acted in accordance with UN resolutions.

North Korea has been hit with fresh UN sanctions to punish it for a nuclear test in May.

The sanctions have been targeted in particular at sales of North Korean arms, a vital export estimated to earn the destitute state more than $1bn a year.

According to US officials the North's biggest arms sales come from ballistic missiles, with Iran and other Middle Eastern states being customers.

Analysts said the UN sanctions and the cut-off of handouts from South Korea have dealt a heavy blow to the North, which has an estimated GDP of $17bn, and may force it back into nuclear disarmament talks in the hopes of winning aid.

The seizure, one of the biggest ever in the international arms embargo against North Korea, also came days after the US president's special envoy made a rare three-day trip to the North on a mission to persuade Pyongyang to rejoin six-nation nuclear disarmament talks.

"There is a possibility that the incident could have a negative effect on moves to get the North to rejoin the six-party talks and a US-North Korea dialogue mood," Yang Moo-jin, a professor at Seoul's University of North Korean Studies, said.