South Korea's parliament introduced a motion Thursday to impeach President Yoon Suk Yeol over a botched attempt to impose martial law, but his party vowed to oppose the move, throwing the process into doubt.

Lawmakers could vote on the bill as early as Friday. Yoon's ruling People Power Party said it would oppose it, but the party has been divided over the crisis. The opposition Democratic Party, which has a majority in parliament, needs at least eight ruling party lawmakers to back the bill for it to pass.

"The Yoon Suk Yeol regime's declaration of emergency martial law caused great confusion and fear among our people," Democratic Party lawmaker Kim Seung-won told a session of South Korea's National Assembly held early Thursday.

Yoon's declaration of martial law late Tuesday attempted to ban political activity and censor the media in South Korea, which is Asia's fourth-largest economy and a key U.S. ally. The shock move divided Yoon's ministers and unleashed six hours of chaos.

None of the 108 ruling party lawmakers was present for the introduction of the impeachment motion. The motion paves the way for a vote to be held in the following 24 to 72 hours.

The impeachment vote followed a night of chaos after Yoon declared martial and armed troops attempted to force their way into the National Assembly building in Seoul, only to stand back when parliamentary aides sprayed them with fire extinguishers.

"The people and the aides who protected parliament protected us with their bodies. The people won, and it's now time for us to protect the people," Kim said. "We need to immediately suspend the authority of President Yoon. He has committed an indelible, historic crime against the people, whose anxiety needs to be soothed so that they can return to their daily lives."

Secretary of State Antony Blinken told Reuters on Wednesday that the U.S. had not been made aware in advance of Yoon's declaration, adding that he anticipated speaking to his South Korean counterpart in the coming days.

Jake Sullivan, President Joe Biden's national security adviser, told Washington's Center for Strategic and International Studies think tank the United States had not been consulted in any way.

"We learned about this from the announcement on television, the same way the rest of the world did," he said. "It raised deep concern for us."

Opposition parties need a two-thirds majority to pass the impeachment bill. If it passes, South Korea's Constitutional Court will then decide whether to uphold the motion – a process that could take up to 180 days.

If Yoon were to be suspended from exercising power, Prime Minister Han Duck-soo would fill in as leader.

If the embattled president resigned or was removed from office, a new election would be held within 60 days.

Yoon told the nation in a television speech late on Tuesday that martial law was needed to defend the country from pro-North Korean anti-state forces, and protect the free constitutional order, although he cited no specific threats.

Within hours, South Korea's parliament, with 190 of its 300 members present, unanimously passed a motion for martial law to be lifted, with 18 members of Yoon's party present.

The president then rescinded the declaration of martial law about six hours after its proclamation.

"There are opinions that it was too much to go to emergency martial law, and that we did not follow the procedures for emergency martial law, but it was done strictly within the constitutional framework," a South Korean presidential official told Reuters by telephone.