SEOUL - South Korea's former president Moon Jae-in said on Friday that prosecutors were becoming political and abusing their power and that his indictment on bribery charges was a good example.

South Korean prosecutors indicted Moon for alleged bribery on Thursday, making him the latest former leader of the country to face legal troubles in a case linked to the employment of his then son-in-law at a Thai airline between 2018 and 2020.

Moon said the indictment against him was unfair and accused the prosecutors of pursuing the case in a predetermined direction.

"Beyond revealing my personal innocence, I plan to focus on properly uncovering and informing the public about the abuse and politicisation of the prosecution's power," he said during a meeting with National Assembly Speaker Woo Won-sik.

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Prosecutors had been investigating whether former lawmaker Lee Sang-jik's appointment as the head of the SMEs and Startups Agency was in exchange for Moon's former son-in-law getting a job and receiving a salary plus living expenses at the Thai-based corporation that Lee controlled, Jeonju District Prosecutors' Office said in a statement.

Lee was indicted for bribery and breach of trust in the case, according to the statement.

In a statement, Moon's lawyers denied the accusations and said what his ex-son-in-law received were salaries for his work.

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They also accused prosecutors of politically targeting Moon ahead of a snap presidential election officially set for June 3 following the impeachment and removal from office of president Yoon Suk-yeol over his short-lived martial law declaration.

Lee Jae-myung, the ex-leader of the liberal Democratic Party (DP), is leading opinion polls with a double-digit gap with candidates from the conservative People Power Party (PPP).

Moon is from the DP, while Yoon is from the PPP.

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Prosecutors referenced previous bribery cases involving former presidents Park Geun-hye and Lee Myung-bak, both of whom were convicted and jailed, as precedents for Moon's indictment.