SEOUL (Reuters) -South Korean investigators again asked the country's acting president on Saturday to order the presidential security service to comply with an arrest warrant for impeached President Yoon Suk Yeol.

The plane crash is the first major test for South Korea’s acting president, Choi Sang-mok, who was appointed the interim leader only on Friday, as the country grapples with a political crisis at the highest levels.

South Korean lawmakers voted on Friday to impeach acting president Han Duck Soo, barely two weeks after Yoon Suk Yeol was removed from the presidency over his imposition of martial law. A total of 192 lawmakers in the opposition-controlled parliament voted to impeach Han - significantly more than the simple majority required.

South Korea's acting President Choi Sang-mok vowed to continue trilateral cooperation with Japan and the United States, saying on Friday his country's diplomacy remains steadfast despite an unprecedented political crisis at home.

South Korea's opposition-controlled National Assembly voted Friday to impeach acting President Han Duck-soo despite vehement protests by governing party lawmakers, further deepening the country's political crisis set off by President Yoon Suk Yeol's stunning imposition of martial law and ensuing impeachment.

The impeachment of Han Duck-soo, acting president since Yoon was impeached on Dec. 14 for declaring martial law, has thrown South Korea's once-vibrant democratic success story into uncharted territory.

South Korea's police have been asked to arrest suspended president Yoon Suk Yeol, the Yonhap news agency reported on Monday. Dozens of investigators working for the Corruption Investigation Office for High-ranking Officials (CIO) attempted to execute a court warrant for Yoon's detention on Friday after he ignored three summonses for questioning over his botched attempt to impose martial law on December 3.

Lee Jae-myung, leader of the Democratic Party of Korea, criticized Acting President Choi Sang-mok, blaming him for the anti-corruption agency’s failure to arrest impeached President Yoon Suk-yeol. “Acting President Choi Sang-mok should be held accountable for disrupting order and acts of insurrection.

South Korean Acting President Choi Sang-mok called for national harmony and unity and for trust in the government in a New Year's address on Tuesday, amid an unprecedented political crisis sparked by impeached President Yoon Suk Yeol's short-lived martial law declaration.