South Korean President Yoon Suk-yeol has been banned from leaving the country over a failed attempt at imposing martial law, amid growing calls for him to step down and a deepening leadership crisis.

Oh Dong-woon, the head of the Corruption Investigation Office for High-ranking Officials, said on Monday he ordered a ban on foreign travel for Yoon when asked at a parliament hearing what actions have been taken against the embattled president.

A Ministry of Justice official, Bae Sang-up, told the committee the travel ban order has been executed.

Yoon’s People Power Party (PPP) staged a walkout of the chamber before a vote to impeach the president on Saturday, prompting accusations of being “accomplices to insurrection” after the motion failed.

On Sunday, PPP leader Han Dong-hoon said Yoon would be excluded from foreign and other state affairs, and Prime Minister Han Duck-soo would manage government affairs until Yoon eventually stepped aside.

The decision to delegate presidential authority to the prime minister has plunged Asia’s fourth-largest economy into a constitutional crisis.

The defence ministry said Yoon was still legally commander-in-chief.

South Korea’s opposition accused the governing party on Monday of staging a “second coup” by clinging to power and refusing to impeach Yoon.

Claiming that the president can remain in office but has delegated his powers to the prime minister and the PPP leader – who is not an elected official – is “a blatant constitutional violation with no legal basis”, Democratic Party floor leader Park Chan-dae said.

“This is an unlawful, unconstitutional act of a second insurrection and a second coup,” Park said, urging PPP to “stop it immediately”.

Yoon has refused calls, including some from within his own party, to resign, and his future looked more uncertain on Thursday when a team at the National Police Agency launched an investigation into the president for alleged treason.

While a sitting South Korean president has immunity from prosecution while in office, that does not extend to allegations of rebellion or treason.

The president gave the military sweeping emergency powers on December 3 to root out what he called “anti-state forces” and obstructionist political opponents. He rescinded the order six hours later, after parliament defied military and police cordons to vote unanimously against the decree.

On Saturday, Yoon issued an apology over the decree, saying he would not shirk legal or political responsibility for the move, which was born of “desperation”.