• South Korea's president, Yoon Suk Yeol, declared martial law in a televised address on Tuesday.
• Lee Jae-myung of the liberal Democratic Party told CNN he thought it was a digital fake.
• Lee went viral after livestreaming himself climbing a fence to get to the National Assembly.

Lee Jae-myung, South Korea's main opposition leader, initially thought the president's martial law declaration was a deepfake.

"I was lying in bed with my wife in our home … when my wife suddenly showed me a YouTube video and said, 'The president is declaring martial law,'" Lee Jae-myung told CNN.

Lee said he was convinced it was a digitally manipulated video.

"I replied, 'That's a deepfake. It has to be a deepfake. There's no way that's real,'" he added.

South Korean President Yoon Suk Yeol shocked the world on Tuesday when he announced he was imposing martial law during a late-night address.

The decree, which enabled temporary military control and the suspension of civilian government activities and civil liberties, was the first since the country's democratization in 1987.

Yoon said the declaration was necessary to prevent subversion by North Korea, South Korea's longtime enemy, but it's likely he was seeking to quash domestic opposition and bolster his power.

He backpedaled six hours later, after the streets were filled with protesters. The decree was voted against by MPs who had to cross barricades and climb walls to make it into the National Assembly.

Lee went viral on social media for livestreaming himself climbing over a fence to the National Assembly building so he could vote against the decree. He described Yoon's move as unconstitutional.

Calls for the president's resignation are growing. According to the Yonhap news agency, all six opposition parties filed an impeachment motion on Wednesday, with a vote set for Friday or Saturday.

Yoon came to power in 2022, narrowly defeating Lee in the most closely contested presidential election in South Korean history.

Since then, his presidency has been riddled with controversy and low approval ratings.

Several senior government figures, including the defense minister, have resigned from their posts.

In the immediate aftermath, the South Korean won plunged as much as 3% relative to the US dollar.