Kim Jong Un
North Korean leader Kim Jong Un gives field guidance to the Fishery Station of the Korean People's Army in this undated picture provided by KCNA in Pyongyang, Nov. 20, 2016. Reuters/KCNA

North Korea has launched an investigation after anti-Kim Jong Un fliers were found in the country, calling to overthrow the leader. According to a report Wednesday, Pyongyang is experiencing domestic instability amid a decline in Kim's popularity.

The state has banned the movement of people after anti-Kim propaganda flyers were found, a source in the country's Yanggang Province said, according to Radio Free Asia (RFA).

The flyers reportedly read, "Let us overthrow Kim Jong Un."

According to the source: "A rigorous probe is taking place ... and in order to track down the suspects handwriting tests are being conducted while people are being interrogated and houses are being searched."

Another source in North Hamgyong Province told RFA that graffiti was found on a building wall in a large marketplace in the city of Chongjin, which read: "Punish Kim Jong Un, the enemy of the people."

The second source added: "Patrol teams blocked the surrounding roads and banned the movement of people after the graffiti was discovered."

Meanwhile, Pyongyang's propaganda outlet Uriminzokkiri reported that North Korean defectors were using drones to target statues of founder Kim Il Sung and leader Kim. Authorities reportedly said that drones were being dispatched across the China border and attacking statues of the "highest dignity."

On Tuesday, reports surfaced that the North Korean leader got drunk during a visit to his summer villa and ordered military leaders to write statements about their failures, according to a Japanese press report.

Kim has been accused of getting carried away with his drinking before. Japanese sushi chef Kenji Fujimoto has said earlier that Kim once drank 10 bottles of expensive Bordeaux wine in one sitting.