SEOUL, June 4 (Xinhua) -- South Korean President Lee Jae-myung formally began his single five-year term after the National Election Commission confirmed his election victory on Wednesday.

Lee assumed the presidency at 6:21 a.m. local time with the election watchdog's approval during a plenary session.

He had no transition period as he was elected in a presidential by-election, caused by his predecessor's botched martial law bid last December.

Lee of the majority liberal Democratic Party won the snap election with 49.42 percent of the vote, beating his major rival Kim Moon-soo of the conservative People Power Party with 41.15 percent.