South Korean Prime Minister Han Duck-soo and senior presidential advisers submitted their resignations to President Yoon Suk Yeol on Thursday following the ruling party's crushing defeat in the parliamentary elections, according to the Yonhap news agency.

In a separate press conference, the leader of the ruling People's Power Party, Han Dong-hoon, said he would also step down to take responsibility for the election defeat.

The results of Wednesday's election posed a huge political blow to President Yoon Suk Yeol, setting back his domestic agenda and leaving him facing an intensifying political offensive by his liberal opponents during his remaining three years in office.

South Korean President Yoon Suk Yeol promised "reform" after a disastrous election Deutsche Welle

What are the election results?

With most of the votes counted, the main opposition Democratic Party and its satellite party appear to have won a combined 174 seats in the 300-member National Assembly, up from 156 in the outgoing legislature.

Near-final results also showed Yoon's conservative People Power Party and its satellite slipping from 114 to 108 seats in parliament, according to the National Election Commission.

The newly formed Rebuilding Korea Party, led by former Justice Minister Cho Kuk, capitalized on dissatisfaction with the two major parties to win 12 seats.

Final official results were expected later Thursday. But the result means liberal opposition forces would expand their control of parliament, although they are unlikely to win a super-majority of 200 seats that would give them legislative power to override vetoes and even impeach the president.