South Korean President Yoon Suk Yeol declared "emergency martial law" on Tuesday, accusing the country's opposition of controlling the parliament, sympathizing with North Korea and paralyzing the government with anti-state activities.

Yoon made the announcement during a televised briefing, vowing to "eradicate pro-North Korean forces and protect the constitutional democratic order." He declared the step as critical in defending the country's constitutional order. It wasn't immediately clear how the steps would affect the country's governance and democracy. 

"I declare martial law to protect the free Republic of Korea from the threat of North Korean communist forces, to eradicate the despicable pro-North Korean anti-state forces that are plundering the freedom and happiness of our people and to protect the free constitutional order," Yoon said.

It is the first time since 1980 that martial law has been declared in South Korea.

The surprise move sent shockwaves through the country, which had a series of authoritarian leaders early in its history but has been considered democratic since the 1980s. The Korean won was down sharply against the U.S. dollar.

The Biden administration is in contact with the South Korean government and is monitoring the situation closely, a White House spokesperson said on Tuesday. 

Entrance to parliament blocked: news agency

Yonhap news agency reported that the entrance to the parliament building was blocked. The agency cited the military as saying activities by parliament and political parties would be banned, and that media and publishers would be under the control of the martial law command.

"Tanks, armoured personnel carriers and soldiers with guns and knives will rule the country," Lee Jae-myung, leader of the opposition Democratic Party, which has the majority in parliament, said in a livestream online.

"The economy of the Republic of Korea will collapse irretrievably. My fellow citizens, please come to the National Assembly."

Yoon — whose approval rating has dipped in recent months — has struggled to push his agenda against an opposition-controlled parliament since taking office in 2022.

Yoon's conservative People Power Party had been locked in an impasse with the liberal opposition Democratic Party over next year's budget bill. He has also been dismissing calls for independent investigations into scandals involving his wife and top officials, drawing quick, strong rebukes from his political rivals.

The opposition has also been attempting to pass motions to impeach three top prosecutors, including the chief of the Seoul Central District Prosecutors' Office, in what the conservatives have called a vendetta against their criminal investigations of Lee, who has been seen in opinion polls as the favourite for the next presidential election, in 2027.

The Democratic Party reportedly called an emergency meeting of its lawmakers following Yoon's announcement.