The seizure in Thailand of some 35 tons of war weaponry from North Korea and the arrest of five foreigners charged with illegal possession of arms may prove a blow to efforts by the United States to negotiate a halt to Pyongyang's nuclear ambitions, observers said.

Thai authorities, reportedly acting on a tip from their American counterparts, impounded an Ilyushin 76 transport plane, carrying explosives, rocket-propelled grenades and components for surface-to-air missiles, during a refueling stop at Bangkok's Don Muang airport Saturday. Four men from Kazakhstan and one from Belarus were detained.

Thai authorities took the action because of a United Nations resolution banning the transport of certain weapons from or to North Korea, Thailand's Foreign Ministry said.

The latest sanctions were imposed in June after the reclusive communist regime conducted a nuclear test and test-fired missiles. The sanctions were aimed at derailing North Korea's nuclear weapons program, but also banned the North's sale of any conventional arms.

The seizure came just days after President Barack Obama's special envoy made a rare three-day trip to North Korea on a mission to persuade Pyongyang to rejoin six-nation nuclear disarmament talks. Envoy Stephen Bosworth said the two sides had reached common understandings on the need to restart the 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 U.S.-North Korea dialogue mood," Yang Moo-jin, a professor at Seoul's University of North Korean Studies, said Sunday.

The chartered cargo plane originated in North Korea's capital, Pyongyang, and requested to land at Don Muang airport to refuel, Thai Air Force spokesman Capt. Montol Suchookorn said.

There were differing local media reports about the plane's destination, with some saying it was headed to Sri Lanka and others saying Pakistan.

"I cannot disclose the destination of their plane because this involves national security. The government will provide more details on this," Supisarn said.

North Korea has been widely accused of violating United Nations sanctions by selling weapons to nations in Africa, Asia and Latin America.

Thailand made the seizure because of the U.N. sanctions, Thai Foreign Ministry spokesman Thani Thongphakdi said.

"Once further details have been finalized, and all the proper checks have been made we will report all details to the United Nations sanctions committee," he said.

The five detained men denied the arms possession charges and were refused bail, Police Col. Supisarn Pakdinarunart said. They were to appear in court Monday.

Local press reports said Thai authorities were tipped off by their American counterparts about the cargo aboard the aircraft. U.S. Embassy spokesman Michael Turner said the embassy would not comment on the incident.

Deputy Prime Minister Suthep Thaugsuban said it would take several days to obtain details on the incident, which would be reported to the United Nations, Belarus and Kazakhstan.

"People should not be alarmed because the government will ensure that the investigation will be carried out transparently. The government will be able to explain the situation to foreign countries," Suthep said.

Thai authorities said the weapons were moved by trucks amid high security Saturday night from the airport to a military base in the nearby province of Nakhon Sawan.

Baek Seung-joo of the state-run Korea Institute for Defense Analyses said the seizure demonstrated a U.S. intention to continue to enforce sanctions on the North while also engaging in dialogue.

Arms sales are a key source of hard currency for the impoverished North. Baek said the North is believed to have earned hundreds of millions of dollars every year by selling missiles, missile parts and other weapons to countries like Iran, Syria and Myanmar.

In August, the United Arab Emirates seized a Bahamas-flagged cargo ship bound for Iran with a cache of banned rocket-propelled grenades and other arms from North Korea, the first seizure since sanctions against North Korea were ramped up.