PYONGYANG, May 10 (Reuters) - North Korean leader Kim Jong Un presided over a mass rally and parade on Tuesday 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.
During the four-day congress, North Korea said it would continue to expand its nuclear arsenal, in defiance of United Nations sanctions, but said it would only use them if it was threatened with nuclear weapons.
Kim also set a five-year plan to revive isolated North Korea's creaking economy, although it was short on targets and the party enshrined Kim's "Byongjin" policy of simultaneous pursuit of nuclear weapons and economic development.
"Under the authorisation of Workers' Party Chairman Kim Jong Un, the Central Committee sends the warmest greetings to the people and soldiers who concluded the 70-day battle with the greatest of victory and glorified the Congress as an auspicious event," Kim Yong Nam, the titular head of state, told the colorful rally under overcast skies in Kim Il Sung Square.
North Korea had been engaged in a 70-day campaign of accelerated productivity in the run-up to the congress, including a sprucing-up of the capital.
For Tuesday's tightly choreographed event, Kim traded the western-style suit worn during the congress for the more traditional uniform of North Korean leaders, a dark jacket buttoned to the collar, and was flanked on a viewing platform by top military and party officials.
"The great leader of Workers Party of Korea, ever-victorious dear comrade Kim Jong Un, manse!," shouted Kim Yong Nam, closing his remarks with an exhortation wishing long life for the 33-year-old leader as the frenzied rally became a parade.
Kim waved vigorously to the crowd and chatted, smiling, with military and party aides from the reviewing stand.
North Korean and Chinese state media carried a message of congratulations to Kim from Chinese President Xi Jinping for his promotion at the party congress.
Relations between North Korea and its main ally China have become frosty over Beijing's growing frustration over North Korea's continued pursuit of nuclear weapons, and China backed tough new U.N. Security Council sanctions in March in response to the North's January nuclear test, its fourth.
There was no direct mention of North Korea's nuclear program in Xi's message.
"We will make efforts together with the DPRK side to bring happiness to the two countries and their peoples and contribute to peace, stability and development in this region by steadily developing the Sino-DPRK friendship and cooperation," North Korea's state KCNA news agency quoted Xi as saying.
DPRK stands for Democratic People's Republic of Korea, the North's official name.
"I wish the Korean people fresh success in carrying out the cause of socialism under the leadership of the WPK (Workers' Party of Korea) headed by Chairman Kim Jong Un," Xi said.
An unusually large contingent of 128 foreign journalists from 12 countries were issued visas to visit the secretive country during the congress, but their access to formal proceedings was limited to a brief visit by a small group to the event venue late on Monday.
BBC correspondent Rupert Wingfield-Hayes and two his colleagues who had been in North Korea to cover the visit of a group of Nobel laureates ahead of the congress were expelled from the country on Monday over his reporting. (Additional reporting by Jack Kim in Seoul and Ben Blanchard in Beijing; Writing and additional reporting by Tony Munroe; Editing by Nick Macfie)