Authorities are investigating a suicide note that allegedly was written by a North Korean soldier who reportedly killed himself in a military base.

The note, posted on the internet, claimed he had shot himself in the head after a disagreement with his commander, according to Yonhap News Agency.

According to Yonap, the military is investigating whether the soldier committed suicide.

The newspaper reported that the soldier reportedly shot himself on August 1 at the base near the border between North and South Korea.

North Korea has denied involvement in the suicide note.

“This is a case of a criminal act and there will be no leniency in our government,” North Korea’s Foreign Ministry spokesman told the Korean Central News Agency (KCNA).

“The Korean people and the Korean peninsula will not be the target of such criminal acts.”

Police are searching for the suspect, who is believed to have been in the military for several years, the newspaper reported.

The Korean government has tightened security at the border since Pyongyang launched its sixth nuclear test in January.

It also stepped up the pressure on North Korea in response to the latest nuclear test.