Inaugurating the ruling Workers' Party congress, Kim hailed "unprecedented results" in the country's nuclear program. Pyongyang claims it tested a hydrogen bomb in January.
Kim told a hall filled with military and party delegates that the hydrogen bomb test and the launch of an earth observation satellite earlier this year had been a "great success."
In the first congress of the ruling Workers' Party in 36 years, he added that North Korea had had taken "magnificent" strides in its nuclear weapons program and would not be cowed by sanctions or international pressure.
Kim's comments contradicted those by most nuclear experts who said data from the H-bomb launch showed it was far too low to be a full-fledged thermonuclear device.
The North Korean leader was interrupted repeatedly by cheers and applause from the 3,400-strong crowd as he laid out accomplishments since he took power in 2011.
The 33-year-old Kim, who was not even born when the last Workers' Party Congress was held in 1980, said the party session would prove to be a "new milestone" that would lay out the future direction "of our revolutionary march".
He also praised the outcome of a recently completed 70-day "loyalty campaign," in which workers nationwide were called upon to put in extra hours to boost output.
Future strategy unveiled?
North Korean state radio said the 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.
Several analysts said they believe the congress will also enshrine Kim's so-called "byungjin" policy of pursuing nuclear weapons in tandem with economic development.
"Kim is after catching two rabbits, a nuclear arsenal and economic development, and he's likely going to declare the country is a nuclear weapons state, so that's one rabbit," said Yang Moo-jin of the University of North Korean Studies in Seoul.
"He might also lay out a five-year or seven-year blueprint for the development of the people's economy," Yang told the Reuters news agency.
In addition, there has been widespread speculation about the North preparing another nuclear test to coincide with the congress, as a defiant gesture of strength and future intent.
More than 100 foreign journalists were invited to cover the congress but they were shown only the outside of the venue before being taken on a visit of the country.
mm/sms (AFP, AP, Reuters)