April 14 (UPI) -- North Korean officers and soldiers suspected of slandering Kim Jong Un are under investigation.
Members of North Korea's second army corps have been placed under arrest for mocking the North Korean dictator, a source in the country's South Hwanghae Province told Radio Free Asia.
"News of cadres of the second army corps slandering Kim Jong Un reached all the way to the People's Army's General Political Bureau, and the arrested cadres are to be severely punished," the source said.
The group had "compared Kim Jong Un to a kindergartner," a joke that began to spread covertly across the military unit, according to the source.
Other soldiers referred to Kim as a mentally ill patient in their jokes, the source said.
Kim is so unpopular among the cadres that another joke, suggesting the North Korean leader is more outrageous than his father Kim Jong Il and grandfather Kim Il Sung combined, refers to him as "Kim squared."
A second source in Yanggang Province said the crackdown began in the second army corps, but other units are becoming nervous.
Soldiers across the military are afraid they may be scapegoated or be targeted in a wave of crackdowns and are staying "prepared for censorship," the source said.
Kim is increasingly unpopular in the country.
In December, anti-Kim propaganda leaflets that read, "Let us overthrow Kim Jong Un" were found in the city of Pochonbo.
The state ordered a crackdown, and conducted handwriting tests while searching homes in order to find the suspects.
Anti-Kim graffiti was also found in the city of Chongjin in December.