Bangkok, Thailand (CNN) -- Thai authorities seized a cargo aircraft carrying tons of weapons from North Korea during a refueling stop in Bangkok, a government official said.
The pilot told Thai authorities the aircraft was headed to Sri Lanka, but its final destination was unknown, according to Panitan Wattanayagorn, a spokesman for the Thai prime minister.
It contained about 35 tons of weapons, including rocket-propelled grenades, shoulder-launched rockets and tubes that may be missile components, the spokesman said.
The plane, which was detained Saturday, had five people onboard -- four from Kazakhstan and one from Belarus. They will appear in court Monday on charges related to illegal weapons smuggling, the spokesman said.
Thai government officials acted after working with several intelligence agencies for several weeks, the spokesman said. The cargo was taken to a military base while the plane, which is registered in Georgia, remains at Don Muang.
Sri Lanka officials said there were no shipments scheduled in the country either by air or sea from North Korea.
"We have asked the Sri Lanka embassy in Bangkok to obtain details from the Thai authorities," the ministry said. "We will have more information on the progress of their investigation later on Sunday."
Such an aircraft could not have landed in any of Sri Lanka's airports without prior authorization, officials in Colombo said.
Last year, two arm dealers were arrested in Thailand. The men's arrest came after a series of events that involved law enforcement agencies from at least five countries, including two undercover agents from the U.S. Drug Enforcement Administration.
Viktor Bout and his associate, Andrew Smulian, made millions of dollars delivering weapons and ammunition to warlords and militants, officials said.
Bout is accused of supplying weapons to war zones around the world -- from Sierra Leone to Afghanistan. He has repeatedly said he has not broken any laws and the allegations against him are lies
A Thai court rejected a U.S. extradition request for Bout in August.
CNN's Dan Rivers and journalist Iqbal Athas contributed to this report.