More than 811,000 people have so far signed the petition, hosted on the National Assembly's website, since it went live on June 20. The petition calls on parliament to introduce a bill to impeach Yoon on the grounds that he is unfit for the job.

In a statement late on Sunday, National Assembly Speaker Woo Won-shik apologised for the disruption, and said parliament would take action to uphold the public's constitutional right.

People trying to access the petition on Monday faced delays that lasted up to four hours. At one point, an error message showed more than 30,000 people were waiting to access the site.

There was no immediate comment from the presidential office.

The petition accuses Yoon of corruption, stoking the risk of war with North Korea and exposing South Koreans to health risks by not stopping Japan from releasing treated radioactive water from the wrecked Fukushima nuclear power plant.

By law, parliament is required to assign any petition signed by more than 50,000 people to a committee which will then decide whether to put it to the assembly for a vote.

But the opposition Democratic Party which holds a majority in parliament is hesitant about turning the petition into an impeachment bill, media reports say, with a spokesperson saying the party has yet to discuss the matter.

The parliament can call for a president's impeachment with a two-thirds majority. The Constitutional Court then deliberates that motion and decides to remove or reinstate the president.

Yoon has been unpopular since taking office in 2022, with his latest approval ratings hovering around the 25 percent mark since April.

South Korea's parliament has twice impeached presidents: Roh Moo-hyun in 2004 and Park Geun-hye in 2017. Roh was reinstated by the Constitutional Court while Park was removed.