The main opposition Democratic Party vowed Friday to reveal the truth behind the recent death of a senior official of the state anti-corruption agency, saying government pressure led to his death.

Until recently, the official of the Anti-Corruption and Civil Rights Commission had served as acting chief of the agency's anti-corruption bureau and oversaw inquiries into politically sensitive cases, including first lady Kim Keon Hee's acceptance of a luxury handbag and opposition leader Lee Jae-myung's use of a helicopter after he came under a knife attack in January.

Speaking to reporters at the National Assembly, DP spokesperson Hwang Jung-a said the official had made a phone call with his acquaintance before his death, complaining of stress and being pressured to close the cases.

During a supreme council meeting, DP Rep. Chung Jung-rae also claimed the Yoon government's "brutality" had caused the official's death.

"It must have been intensely painful for someone who oversaw the anti-corruption bureau, and as a public servant who has done this for over 20 years, to close the cases," DP Rep. Jeon Eun-soo said at the meeting.

The ruling People Power Party expressed regrets over what it described as the DP's attempt to use such an "unfortunate incident" as an opportunity to incite political strife.

"The opposition is framing (the official) as a victim of government pressure when no facts have been confirmed yet," PPP spokesperson Rep. Kwak Kyu-taek said in a commentary.

The official was found dead in an apartment with a suicide note Thursday. (Yonhap)