South Korea's opposition Democratic Party leader Lee Jae-myung on Tuesday called President Yoon Suk-yeol's declaration of martial law in the country an "unconstitutional" decision.

According to South Korea's Yonhap news agency, the leader of the opposition Democratic Party described the martial law decision as an "unconstitutional and anti-people move."

"President Yoon declared martial law for no reason, and soon tanks, armored vehicles and soldiers with guns and swords will take over the country," he added.

Earlier today, South Korean President Yoon Suk-yeol declared "martial law" across the country, accusing the opposition of engaging in anti-state activities.

He explained in a television interview that martial law aims to eliminate pro-North Korean forces and maintain freedom and constitutional order in the country.

Martial law is a set of exceptional rules and measures that a state resorts to under emergency circumstances that allow it to temporarily suspend all or some of the laws in force in it, to ward off the dangers to which the country is exposed.