People pass in front of the building decorated with slogan "The great comrades Kim Il Sung and Kim Jong Il will be with us forever" and their pictures in central Pyongyang, May 3, 2016. REUTERS/Damir Sagolj

North Korea kicked off the first congress of its ruling Workers' Party in 36 years on Friday, with Kim Jong Un expected to further consolidate his control over a country that has grown increasingly isolated over its pursuit of nuclear weapons.

Ahead of the event, secretive North Korea trumpeted "miraculous results" and said advances in nuclear and ballistic missile developments were "the greatest gifts" for the rare party congress, but little of substance was revealed.

On Friday morning, foreign journalists invited to cover the event were not permitted inside the April 25 House of Culture, the stone-built structure draped in red party flags where the congress was expected to run for several days.

Thousands of delegates from around North Korea were expected to attend the first congress since 1980, before 33-year-old Kim was born. Security guards dressed in suits and ties surrounded the venue and dozens of empty buses were parked outside.

Foreign analysts expect the third-generation leader of the Kim dynasty to formally adopt his "Byongjin" policy of simultaneously pursuing nuclear weapons and economic development, and to further consolidate his power.

Byongjin follows Kim's father's Songun, or "military first" policy, and his grandfather's Juche, the North's home-grown founding ideology that combines Marxism and extreme nationalism.

North Korea's state television began its daily broadcast earlier than usual on Friday, with special programming heralding the feats of its leaders.

State radio said the 7th Workers' Party congress would "unveil the brilliant blueprint to bring forward the final victory of our revolution", according to South Korea's Yonhap news agency.

North Korean state media has trumpeted a 70-day campaign of intensified productivity in the run-up to the congress, and Pyongyang has been spruced up for the event.

The state-run KCNA news agency cited advances in nuclear and ballistic missile development, crediting military scientists and engineers for accomplishments that are "the greatest gifts" for the party congress.

"Miraculous results were produced," KCNA said, touting production in the industrial sector that achieved 144 percent of target and electricity generation 110 percent, although the actual targets were not given.

The congress opened on a rainy morning. Covers were hung over the giant portraits of Kim's grandfather, Kim Il Sung, and father, Kim Jong Il, that adorn Kim Il Sung square in the capital, apparently to keep them dry.

Under Kim Jong Un, an informal market economy has been allowed to grow, although it has not been officially adopted as government policy.

However, more taxis and private cars on the streets, more goods in shops, and more buildings under construction attest to growing prosperity and consumption among Pyongyang residents.

Kim has also aggressively pursued nuclear weapons and ballistic missile technology. In March, the U.N. Security Council adopted the latest in a series of resolutions toughening sanctions against North Korea, which conducted its fourth nuclear weapons test in January.

South Korea has been on alert in anticipation that the North could conduct another nuclear test to coincide with the congress.

North Korea's founding leader Kim Il Sung spoke for more than five hours at the last party congress. Kim Jong Il, who almost never spoke in public, did not hold a party congress.