SEOUL (Reuters) - South Korea's acting President Choi Sang-mok said on Friday the government will make an all-out effort to stabilise the economy and will monitor financial markets around the clock to act if needed.

South Korea's acting President Choi Sang-mok said on Tuesday he would immediately move to fill vacancies on the Constitutional Court in a effort to restore stability after the impeachment of two of his predecessors this month triggered political turmoil.

South Korea's Presidential Security Service chief resigned Friday and acting President Choi Sang-mok accepted it. President Yoon Suk Yeol remains in his fortified residence as law enforcement seeks to arrest him.

Republic of Korea is in an unprecedentedly serious situation, Choi said in a written statement, citing changes around global trade, diplomacy and security, as well as domestic political uncertainty

The president's ultraconservative supporters believe that the country has been overrun by North Korea sympathizers conspiring to destroy South Korea's freedoms.

The support rate for South Korea’s main opposition that has been leading the impeachment campaign against President Yoon Suk Yeol dived, as investigators struggle to arrest the embattled leader.

Seok Dong-hyeon, another lawyer advising Yoon, said Yoon viewed the attempts to arrest him as politically motivated and aimed at humiliating him by publicly displaying him in hand

Thousands of South Koreans began gathering in the capital for rival demonstrations on Saturday, as investigators prepare another attempt to arrest suspended President Yoon Suk Yeol over his short-lived martial law decree.