A former Seoul mayor announced his bid Sunday for an upcoming parliamentary election in a political comeback more than four years after he quit his job over controversy surrounding a free school meal policy.

Oh Se-hoon said he will run for the election in Jongno, a key electoral district in Seoul that carries political significance, as a candidate of the ruling Saenuri Party in April.

"It was not an easy decision for me if I care about advantages or disadvantages in an election," Oh said, citing his party's four consecutive election defeats in Jongno over the past five years.

Oh will compete against Park Jin, a former lawmaker, and another former lawmaker for the party's nomination for the April 13 election. Oh, if nominated, will face off against Chung Sye-Kyun of the main opposition Minjoo Party, who currently represents Jongno in the parliament.

Oh resigned from the Seoul mayorship in 2011 after he failed to block an opposition-led free school lunch program in the city's first-ever referendum.

In a country where about one-fifth of its 50 million people live in the capital area, the Seoul mayorship often serves as a key stepping stone for the country's president.

Former president Lee Myung-bak served as Seoul mayor in the early 2000s. (Yonhap)