N Korea congress: Kim Jong-un praises nuclear tests
North Korean leader Kim Jong-un has opened a rare party congress by praising his country's nuclear achievements.
Appearing before thousands of delegates, he said: "Unprecedented results have been accomplished."
This year saw the country announce its fourth nuclear weapon test and that it sent a rocket into space.
The showpiece congress, the first in 36 years, is a chance for the North Korean leader to cement his power.
More than 100 foreign journalists were invited into the country to cover the event but were barred from the April 25 House of Culture, where the party congress is being held.
They were instead taken on a tour round a wire-making factory.
News of Mr Kim's comments came via state television, which showed him on stage speaking to a packed venue.
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"This year... our military and people accomplished great success in the first hydrogen bomb test and (the launch of) the Earth observation satellite Kwangmyongsong-4," Mr Kim said.
"(These events) will be recorded as remarkable achievements."
This is the seventh meeting of the North Korea's Worker's Party and it is being closely scrutinised for any signs of political or economic change.
What next? Stephen Evans, BBC News, Pyongyang
The audience of more than 3,000 of the most senior people in North Korea could not have clapped louder and longer. As they watched their Supreme Leader at Pyongyang's House of Culture, Kim Jong-un eventually gestured to them to stop but still they applauded.
When they did finally stop, he delivered a message of triumph.
The key will now be whether he orders a fifth nuclear test, as he had threatened.
It may be that this Congress is no more than rhetoric designed to cement his position as a strong leader in the eyes of those around him today and those outside the hall, the ordinary people of North Korea.
Few details were released before the congress, but it is due to elect a new central committee, which appoints a Politburo - the central decision-making body of the Communist party.
The appointments will be watched carefully. In 2013 Kim Jong-un had his uncle executed for "acts of treachery" and there have been many reports of purges of high-profile figures.
Some experts have said that Mr Kim's sister Kim Yo-jong is tipped for promotion.
Pyongyang was spruced up ahead of the event, with North Koreans planting flowers and hanging up huge banners with slogans like "Defend the Headquarters of the Korean Revolution at the Cost of our Lives".
No congress was held during the rule of Kim Jong-un's father, Kim Jong-il. His death in 2011 brought Kim Jong-un to power when he was still in his 20s.
The 1980 congress, held before Kim Jong-un was born, saw Kim Jong-il presented as successor to the North's founding leader Kim Il-sung.
Despite his death in 1994, Kim Il-sung, who has been named North Korea's "eternal president'', still officially presides over the latest congress, which is expected to run for several days.