South Korea's main opposition party, the Democratic Party of Korea, said it would initiate impeachment proceedings against President Yoon Suk Yeol unless he immediately resigned, on Wednesday.

This comes after the Korean parliament voted to block President Yoon's motion for the implementation of martial law in the country. 

If Yoon "does not resign immediately, the Democratic Party will immediately initiate impeachment proceedings in line with the will of the people," it said in a statement.

Yoon's own party, the People Power Party, has described the president's attempt to impose martial law as "tragic." The party also called for those involved in the move to be held accountable. 

"The president must directly and thoroughly explain this tragic situation," People Power Party leader Han Dong-hoon told reporters in a televised broadcast, adding that "all those responsible must be held strictly accountable."

Read more: South Korea parliament rejects president's martial law declaration

Charges of insurrection to be filed against Yoon

The opposition later announced that it would file charges of insurrection against Yoon, his defense minister, interior minister, and other key military and police figures involved in carrying out the martial law orders.

Senior aides working for Yoon also offered to resign en masse, according to the Yonhap News Agency.

"Yoon's senior aides offer to resign en masse over martial law declaration," Yonhap said,.

Swiftly dismantled martial law

Earlier on Tuesday, Yoon imposed "emergency martial law", accusing the opposition of dominating the parliament, sympathizing with the Democratic People's Republic of Korea (DPRK), and crippling the administration through anti-state acts.

The parliament speaker called the martial law notification unconstitutional, and parliamentarians voted early Wednesday to reject it. A few hours later, Yoon backtracked on his decision and said he would repeal it. However, he continued to criticize parliament’s attempts to impeach key government officials and senior prosecutors and lawmakers’ "unscrupulous acts of legislative and budgetary manipulation that are paralyzing the functions of the state."

The helmeted military was seen on TV during the night, reportedly entrusted with implementing martial law, attempting to enter the assembly building, as legislative aides used fire extinguishers to drive them back.

Yoon made the declaration during a televised conference, promising to "eradicate pro-DPRK forces and protect the constitutional democratic order."

Politicians, including the head of his own conservative party, Han Dong-hoon, immediately opposed the action, calling it "wrong" and vowing to "stop it with the people." Eventually, Yoon's orders were quickly dismantled as opposition grew from within his party, among Koreans, and other entities including workers' unions. 

Read more: 'Rehearsals for invasion: DPRK on latest S. Korea, US joint drills