Seoul, Dec 9 (IANS): South Korean President Yoon Suk Yeol was placed under a travel ban on Monday pending an investigation into treason and other charges related to his short-lived imposition of martial law last week, with political turmoil deepening over Yoon's political future.

The ban was imposed by the justice ministry shortly after the Corruption Investigation Office for High-ranking Officials (CIO) said it had submitted a request for the order.

Yoon has been booked as a suspect in simultaneous investigations conducted by the police, the prosecution and the CIO over his surprise declaration of martial law on last Tuesday, Yonhap news agency reported.

The order was lifted six hours later after the National Assembly voted to end it.

The main opposition Democratic Party and other opposition parties also submitted a motion to impeach the president afterwards, but it was scrapped on Saturday after all but three lawmakers of the ruling People Power Party boycotted a vote on it.

Bae Sang-eop, a senior immigration official at the justice ministry, told lawmakers during a parliamentary hearing Monday that a travel ban is almost always issued following a simple review of the formal requirements.

He said the ban had been imposed on Yoon sometime after 3 p.m.

CIO chief Oh Dong-woon told the hearing his office is committed to carrying out a thorough investigation into "the leader and key offenders related to treason" with the suspects under physical detention, in principle.

When asked if the CIO had requested a travel ban on First Lady Kim Keon Hee, he said it would be reviewed.