The Russian-made plane, believed to have had about 20 people on board, left from the capital, Vientiane, early this morning headed for an official ceremony in the northeastern province of Xiangkhoung, about 470 kilometres away, said Thai Foreign Ministry spokesman Sek Wannamethee.
It crashed in a forested area of Xiangkhoung province, near one of Laos' major archaeological sites, the Plain of Jars.
Among those confirmed killed in the crash were Defence Minister Douangchay Phichit and his wife, said Nipat Thonglek, the Thai defence ministry's permanent secretary.
Also killed were the governor of the capital of Vientiane, Sukhan Mahalad, and two other senior officials, Nipat said. He said he was given the information by authorities in neighbouring Laos who did not immediately release details of the other passengers.
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The cause of the crash was not immediately known.
Lao National Television showed images of the aircraft in a wooded area with smoke rising from its badly charred remains.
Thailand's Thai Rath newspaper identified the plane as a Russian-made Antonov AN-74.