Kim Jong-un promoted to chairman of North Korea's ruling Workers Party

His predecessors will keep their posthumous titles of 'eternal general secretary' and 'eternal president'

Kim Jong-un had already been head of the party, but with the title of first secretary (Ed Jones/AFP/GettyImages)

Kim Jong-un has been named chairman of the Workers' Party of Korea at a rare party congress held in Pyongyang.

The first congress of the Workers' Party in 36 years, which opened on Friday, was scheduled to promote Kim to the "top post" of the party, according to state media.

During the congress, Kim Yong-nam, head of the North's parliament, read a roster of top party positions, calling Kim Jong-un Chairman of the Workers' Party of Korea for the first time.

Kim had already been head of the party, but with the title of first secretary.

His predecessors will keep their posthumous titles. Kim Jong-Il remains "eternal general secretary" and Kim Il-Sung is still "eternal president".

The congress, which began Friday, has celebrated Kim's successes on the nuclear front and promised economic developments to boost the hermit nation's standard of living.

However, the congress has mostly put Kim front and centre in the eyes of the people and the party as the country's sole leader.

On Sunday, Kim Jong-un delivered a three-hour speech to delegates to review the country's situation and progress since the last congress was held, in 1980, before Kim was born.

He announced a five-year economic plan, the first made public since the 1980s.

During the speech, he said North Korea was a responsible nuclear state and said it would not use its nuclear weapons first, unless its sovereignty was threatened.

The speech underscored Kim's dual focus on building up the country's military while trying to kick-start its economy, which has seen some growth in recent years but remains hampered by international sanctions over its nuclear program.

Additional reporting by AP