China's Xi congratulates North Korea's Kim on party promotion

Students carrying party flags shout slogans as they march past North Korean leader Kim Jong Un during a mass rally and parade in the capital's main ceremonial square, a day after the ruling party wrapped up its first congress in 36 years by elevating him to party chairman, in Pyongyang, North Korea, May 10, 2016. REUTERS/Damir Sagolj

PYONGYANG (Reuters) - Thousands of ecstatic North Koreans joined a mass rally and parade on Tuesday as leader Kim Jong Un capped off the consolidation of his power at a ruling party congress at which he formalised its claim to be a nuclear weapons power.

Kim used the party congress, the first in 36 years, to highlight North Korea's aim to expand its nuclear arsenal, in defiance of U.N. sanctions, though he said the weapons would only be used if North Korea was threatened with similar weapons.