Tens of thousands of South Koreans from across the country gathered in the streets outside the National Assembly in Seoul on Saturday, demanding President Yoon Suk Yeol’s ouster. Mr. Yoon briefly imposed martial law on Tuesday, reopening old wounds and plunging the country into political chaos. An attempt to impeach Mr. Yoon failed to garner the required number of votes, prolonging the political upheaval and uncertainty that has roiled the country this week.

Protests in the city and around the country have intensified since Mr. Yoon’s audacious move on Tuesday. The rally at the National Assembly ahead of the impeachment vote on Saturday was the largest one yet, despite freezing temperatures. By 3 p.m. the areas in front of the National Assembly were filled.

People waved flags representing labor unions, human rights groups and smaller political parties. The police, wearing neon jackets, were lined up along the crowds to keep order.

As the grand boulevard facing the National Assembly filled up with protestors, people moved to the street that runs across the front of the complex.

Meanwhile, in another part of Seoul, supporters of Mr. Yoon gathered near Gwanghwamun Square. There were chairs set up for the supporters, unlike the crowds sitting on the ground outside of the National Assembly. Soon after the impeachment vote began, speakers were quick to announce that impeachment looked unlikely, and the crowd turned jubilant.

Protesters in front of the National Assembly stayed well into the night, as the voting session dragged on. People held candles and colorful light sticks. South Korea has a tradition of holding candlelight rallies to express political dissent.

As 9 p.m. approached, it became clear there were not enough votes to impeach Mr. Yoon and the crowd began to thin out.

However, many protesters said they would not give up. “I plan to come every weekend,” said Subin Park, 29, who had traveled from Bucheon, west of Seoul. “I hope a lot of people will show up from Monday.”