S Korean investigators summon Yoon for questioning over martial law

South Korea's law enforcement authorities on Monday said they have summoned impeached President Yoon Suk Yeol for questioning this week over charges of insurrection and abuse of power related to his failed attempt to impose martial law earlier this month.

The joint investigation team, consisting of the police, the Corruption Investigation Office for High-ranking Officials, and the defence ministry's investigation unit, said it would seek Yoon's presence for questioning on Wednesday, the Yonhap news agency reported.

On Saturday, South Korea's parliament voted to impeach Yoon, almost two weeks following his botched attempt to institute martial law.

Prime Minister Han Duck Soo is to assume presidential duties until the Constitutional Court takes the final decision on whether to confirm Yoon's impeachment or declare it unconstitutional.

Meanwhile, the leader of Yoon's People Power Party (PPP), Han Dong Hoon, resigned from the role on Monday.

"I am stepping down as the leader of the People Power Party," Han told a press conference. "It has become impossible to carry out my duties as party chief due to the collapse of the party's Supreme Council."

Han first said he would back the impeachment of Yoon, but then backtracked, before going on to openly declare his support for ousting the president.

The opposition has accused Yoon of violating the constitution after his unexpected declaration of martial law on December 3.

The move shocked the nation but was rescinded just hours later following massive public resistance.

Yoon, in a televised address on Thursday, labelled his political opponents "anti-state forces." He said that he had declared martial law to protect the nation.