A prosecutor under investigation for interfering with a high-profile probe into the state spy agency's illegal political activities died Monday in an apparent suicide, Seoul prosecutors' office said Monday.

Byun Chang-hoon, a prosecutor at the Seoul High Prosecutors' Office, jumped off a four-story building in southern Seoul around 2:30 p.m., the office said.

He was transferred to a nearby hospital and pronounced dead about two hours later, it said. There was no suicide note. 

Byun was set to appear in a court hearing to review the prosecution's request for his arrest for alleged involvement in a cover-up of election meddling by the National Intelligence Service in the run-up to the 2012 presidential vote.

Prosecutors have been widening their probe into illicit cyberoperations by the NIS aimed at swaying public opinion in favor of the then Lee Myung-bak government.

When the prosecution began its first probe into the NIS scandal in 2013, Byun had been dispatched to the spy agency as a legal advisor. The NIS assigned him to a task force to deal with the prosecution probe and court proceedings.

Byun is accused of setting up bogus cyberoperation offices and making fake documents to conceal NIS agents' political activities and instructing cyberteam crews to lie to the prosecution and court.

Last month, Byun was demoted to a lower post from a senior-level position at the Seoul Northern District Prosecutors' Office after he became a subject in the investigation.

He and two other ranking prosecutors faced court hearings on their arrest warrants. (Yonhap)