Confusion continues in South Korea over the failure of an impeachment motion against President Yoon Suk-yeol.

A senior official of the South Korean prosecutors' office says Yoon is being investigated for alleged treason and abuse of power.

Crowds gathered in front of the National Assembly in Seoul on Sunday after the impeachment motion failed due to a lack of voters.

A woman said: "I doubt that a president who cannot take responsibility for his actions can stay in office. I wonder if he feels ashamed of himself."

A man said, "Yoon should be impeached and the ruling party should be dissolved."

Former Defense Minister Kim Yong-hyun was reportedly detained on Sunday, after presenting himself for questioning by prosecutors. He allegedly advised Yoon to declare martial law.

Interior and Safety Minister Lee Sang-min offered to step down on Sunday.

Lee said in a statement that he sincerely recognizes his responsibility for not adequately assisting Yoon and he apologizes to the people.

The presidential office said Lee's resignation had been accepted.

The prosecutors' office says they have received many complaints about Yoon's martial law declaration. It also says Yoon is being investigated on suspicion of treason and abuse of power.

Ruling party leader Han Dong-hoon released a joint statement with Prime Minister Han Duck-soo.

Han says his party intends to settle the turmoil and stabilize the political situation by quickly realizing Yoon's orderly resignation.

He says the president will not take part in state affairs, including diplomacy.

The leader of the largest opposition Democratic Party, Lee Jae-myung, says if the prime minister and the head of the governing party take over state affairs without any constitutional or legal grounds, this would constitute a "secondary rebellious act." He says they will definitely carry out Yoon's impeachment.

The Democratic Party plans to submit another impeachment motion against Yoon.