North Korea has put four officials in prison. This is because a navy ship they launched did not work well. Their leader, Kim Jong Un, said it was their fault because they were not careful. State news reported this.

North Korea does not often punish its officials in public for failed weapon tests or military events. The arrest of four officials this weekend shows that Kim is very serious about making his army stronger and improving control in the country.

On Wednesday, a large ship called a destroyer was damaged. Kim was there when it happened. A part at the back of the ship broke off during a launch event. This was at a port in Chongjin. Pictures from space showed the ship on its side. It had blue covers on it, and some parts were under the water.

Kim was very angry about what happened. The warship is very important for his plan to make his navy better. He quickly said that military officers, scientists, and shipyard workers were responsible. He called it a "bad mistake because they were not careful and did not think in a scientific way."

On Monday, the Korean Central News Agency said that the police arrested Ri Hyong Son. He works for the Workers Party and said he was very sorry because the rocket launch did not work.

On Sunday, KCNA said that three officials from Chongjin Shipyard were arrested because of the problem. They were the main engineer, the person who leads the ship's body construction, and the assistant manager for office work.

Hong Kil Ho, the shipyard manager, also had to answer questions. KCNA news said this before.

On Thursday, North Korea's Central Military Commission told investigators that the people who did this must take responsibility. But it is not clear what will happen to the officials who were arrested.

When Kim first became leader, he was known for killing many important people, even his uncle. People think he did this to make his power stronger and get rid of anyone who could be a danger. Recently, there have not been many reports of these killings. This is because Kim now has complete power, like his father and grandfather had.

Kim has given special help to scientists and engineers who work on weapons. He wants to make more nuclear weapons and missiles. He gave them new apartments in Pyongyang. Last year, a military spy satellite did not launch well. After this, he told his scientists that he supported them. He said that "you always need to fail before you can succeed." State media reported this.

Experts say Kim wants to make good progress on his five-year plan to build weapons. He started this plan in early 2021. Kim has said that North Korea needs a stronger navy, missiles that can carry nuclear weapons, and other modern weapons. He says this is to deal with the increasing threats from the U.S. and its friends.

Last month, North Korea launched a new, large ship. It is a warship that weighs 5,000 tons. They celebrated this event a lot. This ship is their biggest and best warship. News reports said it can carry different weapons, like nuclear missiles. Kim said building it was a very important step for North Korea's navy.

North Korea said that the second ship wasn't badly damaged. They said the side of the ship had some scratches and a little water got into the back part.

North Korea said on Friday that it needed about 10 days to fix things, but many people thought the damage was probably worse.