Prosecutors are currently focusing on bribery allegations that some of conglomerates donated tens of millions of US dollars to two nonprofit foundations controlled by Choi Soon-sil in return for receiving business favors.

President Park logged a zero support among voters in their 20s and 30s. The approval rating in the North Gyeongsang province, a political home turf for Park and her ruling party, plunged to 3 percent. It was lower than the average approval scores.

With the falling popularity of the president, support for Park's ruling Saenuri Party tumbled to 12 percent, the lowest since it was created in 1997.

The biggest opposition Minjoo Party ranked first with a support score of 34 percent, followed by the casting vote-wielding opposition People's Party with 16 percent.

Division within the Saenuri Party deepens as some of former and incumbent lawmakers seceded from the party earlier this week. The party leadership has rejected calls for resignation, made by many of non-President Park faction members.

Kim Moo-sung, former chairman of the governing party, declared a plan this week to join a campaign by three main opposition parties to impeach President Park.

An impeachment motion requires at least two-thirds of the 300-seat National Assembly to be passed through the parliament. Around 40 legislators in the ruling party, which has 128 parliamentary seats, decided to vote for the impeachment, according to local media reports.