President Yoon Suk Yeol's approval rating fell by 7.7 percentage points to 17.3 percent in the first week of December due to his abrupt imposition of martial law, the biggest threat to South Korea's democracy in the 21st century, a poll showed Monday.

In the meantime, Yoon has not appeared in public for three days since he delivered a televised address on Saturday promising that he would entrust his executive powers to his People Power Party. The presidential office has been almost non-functioning, with no plans announced for any press briefings or statements. The office also remains silent on developments in related investigations and on Yoon's plan to hand over his role to the ruling party.

According to a Realmeter poll of 1,012 respondents, the conservative president's approval rating hit its lowest point since his inauguration in May 2022. Monday's poll marked the first time Yoon's presidential approval rating, estimated by Realmeter, has fallen below 20 percent.

The poll also found a decline in approval of 13.6 percentage points among respondents who identified themselves as conservatives.

Yoon's overall approval rating fell below the record low of 22.3 percent set in the first week of November, according to Realmeter. That poll was conducted immediately after the release of a phone call recording between Yoon and his estranged political consultant Myung Tae-kyun, which indicated Yoon might have interfered in the ruling People Power Party's election process after a backroom deal with Myung.

Disapproval of Yoon rose 8.2 percentage points to 79.2 percent, reaching an all-time high.

Monday's poll also indicated that more South Koreans leaned toward the main opposition Democratic Party of Korea and fewer identified themselves as supporters of the People Power Party.

The Democratic Party's lead -- by 21.2 percentage points -- was the largest since Yoon took office 2 1/2 years ago, according to Realmeter.

Those who approved of the main opposition party came to 47.6 percent, up 2.4 percentage points, whereas those who supported the ruling party stood at 26.2 percent, down 6.1 percentage points.

Earlier on Friday, a separate Gallup Korea poll showed that Yoon's job approval rating fell by 6 percentage points to 13 percent, hitting an all-time low after the martial law declaration, and his disapproval rating surged to 80 percent.

The lowest approval rating ever recorded by the weekly Gallup Korea poll, which began in 2012, was for former president Park Geun-hye -- whose five-year term ended early due to impeachment.

As a massive corruption scandal came to the fore, Park saw her approval rating fall to just 4 percent in November 2016 in the days before her impeachment by the National Assembly. The Constitutional Court finalized Park's impeachment in March 2017.

Yoon is facing the ongoing threat of impeachment as the opposition-controlled National Assembly pledged to file a motion to impeach the president every week, amid political gridlock over the ruling bloc's proposal to have Yoon's presidential powers handed over to the government and the People Power Party.