The latest in a series of massive anti-Park demonstrations in the South Korean capital came just hours after opposition parties filed an impeachment motion that will be put to a vote by MPs yesterday.
Whether the motion is adopted or not, Park is firmly on course to become the first democratically-elected South Korean president not to complete a full, five-year term.
The 64-year-old stands accused of colluding with an old friend who has been formally indicted for attempted fraud and abuse of power.
The protestors who have taken to the streets in their millions in recent weeks want her out immediately, but the political establishment is struggling to find a similar unity of purpose.
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The impeachment motion introduced in the early hours of Saturday morning carried 171 signatures -- accounting for every legislator from the three opposition parties and independents.
In order to secure the two-thirds majority required for impeachment in the 300-seat national assembly, it will need the support of more than two-dozen lawmakers from Park's ruling Saenuri Party.
The party has now proposed she resign in April -- a timeline it justifies as more conducive to a calm and steady preparation for an early presidential election.
Observers say the Saenuri rebels are likely to fall in line with the proposal and vote against the motion on Friday -- much to the opposition's annoyance.
"If the motion fails to pass due to a lack of cooperation from the ruling party, it must take responsibility for all the consequences", the main opposition Democratic Party's floor leader Woo Sang-Ho said.
"Park is lying when she said she would step down voluntarily. Impeachment is the only option left for stripping her of the office," said Goh Du-Hwan, a 45-year-old accountant.
Goh was among hundreds of activists who gathered for an early protest outside the Saenuri Party headquarters ahead of Saturday's mass rally.