New Delhi, June 3 -- Liberal opposition leader Lee Jae-myung has been elected president of South Korea, the country's National Election Commission has officially declared, following a decisive victory in a snap election triggered by the impeachment of his predecessor, Yoon Suk Yeol, over a failed attempt to impose martial law.

Lee secured 49.3% of the vote, defeating Kim Moon-soo of the conservative People Power Party (PPP), who garnered 41.3%, with over 99% of ballots counted.

"I humbly accept the people's choice," Kim told journalists, conceding defeat even before the final tally. "I congratulate President-elect Lee and wish him success."

Lee's victory brings to an end months of political upheaval triggered by the short-lived martial...