In South Korea, candidates from the largest opposition party have won mayoral elections in Seoul and Busan. The races are seen as a bellwether for next year's presidential vote, piling further pressure on President Moon Jae-in.

Oh Se-hoon of the largest opposition People Power Party won 57.5 percent of ballots cast in Seoul on Wednesday, comfortably beating Park Young-sun of the governing Democratic Party by a margin of about 18 points.

In the second-largest city of Busan, opposition candidate Park Heong-joon thrashed the governing party candidate by some 28 points.

The elections took place amid growing criticism of public officials in South Korea over allegations of illegal land deals as real estate prices soar.

Approval ratings for President Moon have tumbled to the 30 percent level -- record lows since he took office in 2017.