Kim Jong Un boasted “unprecedented accomplishments” in nuclear and missile tests this year as he convenes the first congress of the country’s Worker’s Party in 36 years. The Washington Post’s Anna Fifield reports from Pyongyang, North Korea. (Jason Aldag/The Washington Post)

Kim Jong Un, the third generation of North Korea’s ruling dynasty, boasted Friday of “magnificent and exhilarating” advances in nuclear and missile capabilities this year as he convened the first congress of the country’s Workers’ Party in his lifetime.

The congress — the first held since 1980, three years before Kim was born — essentially amounts to an extravagant, state-choreographed spectacle built around Kim’s leadership.

The intent was clear with each round of rapturous applause for the 33-year-old leader: a display of loyalty and bolstered legitimacy for his rule even as North Korea’s defiant policies bring further isolation and pressures.

But Kim wasted no time in taking another swipe. His bravado was aimed directly at the international community amid alarm over the North’s attempts at military and nuclear expansion.

“In this year of the seventh party congress, the military and the people have accomplished great success in the first hydrogen bomb test and the launch of an Earth observation satellite . . . to brilliantly illuminate the prowess of Juche Korea,” Kim said, referring to North Korea’s unique ideology that translates as “self-reliance.”

“Unprecedented results have been accomplished,” Kim, wearing a Western-style suit and tie instead of his usual Mao suit, told a packed audience in the ostentatious April 25 House of Culture in central Pyongyang.

Kim ordered North Korea’s fourth nuclear test in January, an event he hailed as “historic” in Friday’s address. Pyongyang claimed to have tested an exponentially more powerful hydrogen bomb, but outside analysts said it appeared to have been a lesser atomic device, similar to the North’s previous test.

In February, Kim then oversaw the launch of what authorities said was a rocket intended to put a satellite into orbit but outside analysts widely believe to be part of an intercontinental ballistic missile program aimed at enabling North Korea to potentially strike the continental United States.

But other launches since, including two intermediate-range missile launches and another from a submarine, were deemed by the United States and South Korea to have failed. There was no mention of this in Kim’s triumphant address, however.

Still, Kim’s boasts seem to prove the theory that this year’s provocations — from the nuclear and missile tests to threats to blow up New York and Washington — were part of an effort to bolster the young leader’s legitimacy.

The city of North Korea’s elites and loyal party members, Pyongyang, is hosting the congress of its ruling Workers’ Party for the first time in 36 years. (Jason Aldag,Anna Fifield/The Washington Post)

“He followed the general outline of ‘aren’t we great’ and paying tribute to his father and grandfather, and to the Workers’ Party leadership,” said Michael Madden, who runs the North Korean Leadership Watch blog. “He was saying we have a strong and prosperous fatherland and we’re not going to be bullied by big countries.”

The authorities in Pyongyang allowed in about 130 foreign journalists, including three from The Washington Post, to cover the event, apparently wanting to make sure their message was disseminated to a wide audience.

But the journalists were not permitted to enter the building where the congress was being held Friday and were instead deposited by their government minders on a street corner some 300 yards from the red-festooned venue.

After an hour, they were taken back to their hotel, where state television was running dramas centered on revolutionary heroes. Even as the congress continued across town, the journalists were then taken to an electrical cable factory.

It wasn’t until 10 p.m. that news of the congress was shown on television, with Kim’s speech and the orchestrated cheering supplemented with photos of Kim in a variety of military situations, looking happy.

Details remain scarce. It is not clear when the congress will end or what else will be on the agenda. Thousands of people have been on the streets of Pyongyang in the rain, practicing for a torchlight parade, but no date for the event has been given.

North Korea has placed huge importance on the congress. Previous such events have served as forums to show the ruling party’s strength and have occasionally been used as vehicles for major announcements. Kim Il Sung, the “eternal president” of North Korea and the grandfather of the current leader, used the 1980 congress to unveil his son, Kim Jong Il, as his successor. Kim Il Sung died in 1994 and Kim Jong Il in 2011.

Following in his grandfather’s footsteps, Kim Jong Un has elevated the status of the Workers’ Party and has effectively moved away from the “military first” policy promoted by his father by announcing a “simultaneous push” toward both nuclear and economic development.

Analysts say that by calling the congress, Kim is continuing this pattern of increasing the stature of the party, while at the same time bolstering his claim on the leadership. North Korea is home to the world’s only communist dynasty, and Kim Jong Un was not even 30 when he became its third-generation leader.

Korean culture is Confucian and places a premium on age and seniority, but Kim is a good ­half-century younger than some of his advisers. The regime also was unable to lay the kind of groundwork for the current leader that it did for Kim Jong Il.

Kim Jong Il was in the public eye, moving through a series of official positions, for more than two decades before he took the reins after Kim Il Sung’s death. But there was barely more than a year between the announcement of Kim Jong Un as successor and his accession to the North Korean throne.

As a result, few analysts were expecting bold initiatives to be unveiled at this congress, given the difficulty the Kim regime has had making good on many of its promises. Instead, they were expecting pronouncements about the strength of the party.

The authorities here had instituted a “70-day speed battle” to prepare for the congress, requiring all citizens to work from 5:30 a.m. until well after dark, seven days a week, painting buildings, paving roads and planting gardens. Streets have been decorated with banners and red Workers’ Party flags, and thousands of people have been practicing for parades.