Son, the top seed, has not won a tournament since rising to the top of the rankings in May.

He looks well placed at the SK Handball Stadium in Seoul but the 29-year-old South Korean needed three games before managing to oust Indian qualifier Parupalli Kashyap.

In the end it was a 21-16, 17-21, 21-16 victory for Son as he reached the quarter-finals.

The bronze medallist at last month's World Championsips in Glasgow should feel confident of victory as most of the main challengers are no longer in contention.

Second seed Lee Chong Wei of Malaysia, a triple Olympic silver medallist, withdrew before play began alongside Denmark's third seed and world champion Viktor Axelsen.

Hong Kong's sixth ranked Angus Ng was his nearest seeded challenger but he lost his second round clash to Indonesia's Anthony Sinisuka Ginting, 21-18, 21-18.

Seventh seed Wang Tzu-wei of Chinese Taipei did progress, beating Indian B. Sai Praneeth 21-13, 26-24.

In the women's competition at the Super Series event, top seed Tai Tzu-ying of Chinese Taipei was knocked out.

The world number one fell in three to Minatsu Mitani of Japan, 23-21, 14-21, 21-18.

Japan's world champion and eighth seed Nozomi Okuhara went through after a 21-16, 21-13 win over team-mate Sayaka Sato.

India's PV Sindhu, the silver medallist at both Rio 2016 and the World Championships, beat Thailand's Nichaon Jindapon 22-20, 21-17.

Quarter-finals will be played tomorrow.