SEOUL (AFP) - The impeachment of South Korea's embattled President Park Geun Hye in a snowballing corruption case inched closer on Monday (Nov 21) when the main opposition party said it was examining its options.

The move comes the day after prosecutors named Ms Park a criminal suspect in a major influence-peddling case, tightening the noose on an already hugely unpopular leader.

"We will immediately review the timing and methods of impeachment and set up a subcommittee to review a push for impeachment," said Ms Choo Mi Ae, head of the opposition liberal Democratic Party.

Two smaller opposition parties have already said they will seek to remove her.

Lawmakers have been under growing public pressure to oust Ms Park, with weekly mass protests drawing hundreds of thousands of protesters across the country.

But with impeachment proceedings likely to drag on for months, the Democratic Party has been reluctant to move because of fears of a backlash from conservative voters.

On Sunday, Seoul prosecutors said Ms Park had colluded with her long-time friend, Choi Soon Sil, who is accused of coercing local firms into donating more than US$60 million (S$85.6 million) and of meddling in state affairs.

Ms Park's single, five-year term ends in February 2018, and observers say she is likely to do all she can to serve out her time because a sitting president cannot be charged with a criminal offence except insurrection or treason.

The three opposition parties hold a combined 55 per cent of parliamentary seats - short of the two-thirds majority required to pass an impeachment Bill.

But dozens of lawmakers in Ms Park's own party vowed on Sunday to support a push for her impeachment, wary of growing public anger about the scandal.