North Korean leader Kim Jong-un has dismissed a vice premier in charge of the country’s machine-building industry and criticized officials as “irresponsible” in a rare move ahead of a key party congress.

The state-run Korean Central News Agency reported on the situation Tuesday, saying Kim gave a speech to mark the completion of the first-stage modernization project at the Ryongsong Machine Complex on Monday and fired Vice Premier Yang Sung-ho “on the spot,” blaming him for setting the project back and causing economic losses.

Kim called the project an important one that will have a big impact on the national economy, but said it made a bad start because of irresponsible, rude and incompetent officials.

The North Korean leader also accused Yang of attempting to mock the party plenary meeting and said he was unqualified for the post, according to the report.

Kim said promoting Yang to vice premier was a mistake and likened the decision to hitching a goat to an ox cart. 

Yang, who served as machinery industry minister before taking charge of the machinery sector, is also an alternate member of the party’s Politburo.

His sudden and public firing is seen as a bid to strengthen discipline among senior officials ahead of the upcoming ruling Workers’ Party of Korea’s ninth party congress, which is expected to take place next month. 

Experts predict the regime will outline its economic development vision at the party congress and conduct a major personnel reshuffle afterward.