The country had just closed all nightclubs and churches to curb a new wave of infections.
South Korea's parliament was shut on Thursday after a photojournalist covering a meeting of the ruling Democratic Party tested positive for COVID-19.
Authorities have also closed the building where the National Assembly, the country's 300-member unicameral legislative body, is located.
Ten Democratic Party officials, including the president and the parliamentary leader, will undergo screening tests and be placed in self-isolation.
This is the second closure of parliament due to the coronavirus, with the first one occurring in February.
South Korea, after having initial success in halting the virus spread, is now battling a second coronavirus wave, with several new outbreaks linked to churches.
Authorities on Thursday reported the largest daily increase in cases in six months - 441 new cases, most of them in the greater Seoul area, where half of the country's population of 52 million live.
The number of new infections exceeded one hundred for the 14th consecutive day, bringing the national toll to over 18,000 since the start of the pandemic.
In an effort to curb the new outbreak, authorities ordered last week the closure of all night clubs and churches.
