PYONGYANG, North Korea — North Korea opened the first full congress of its ruling party since 1980 with leader Kim Jong Un speaking behind closed doors to thousands of cheering delegates.

The congress is a major political milestone for the young North Korean leader, who was not yet born when the previous congress was held 36 years ago.

Kim, who stood as he read the prepared speech to the more than 3,400 delegates, was interrupted repeatedly by cheers and applause as he declared the congress open and laid out accomplishments since he took power in 2011 — including what the government says was its first hydrogen bomb test in January.

Officials portrayed the meeting as a showcase of the country’s stability and unity under Kim despite international criticism and tough new sanctions over its nuclear and missile programs.

North Korea’s information committee bused more than 100 foreign journalists to the congress venue for a look, but only from the outside, at the ornate April 25 House of Culture, draped in red party banners and flags.

Officials had another surprise as the day wore on for the news-hungry media guests — brought in to give the congress a global audience — who were then taken not to the meeting, but to a wire factory.