Leung, 36, the defending champion, got there after winning two of three group matches. His only loss was to 44-year-old Brazilian Eliseu dos Santos.

Leung, in his fifth Paralympics, established a four-point lead in the first two ends, but dos Santos made a successful comeback in the final two ends to win 6-4 against the opponent who thrashed his elder brother, Marcelo, 48, by 14-0 in a group match.

Leung also defeated Sergey Safin of the Russian Paralympic Committee 3-1.

Having bagged three gold medals in past Paralympics, Leung will be playing 26-year-old Michaela Balcova from Slovakia, a gold medalist in the pairs in the 2016 Rio Paralympics, in the quarterfinals.

His partner in the pairs later, 42-year-old Lau, was in top form after beating world No 1 Alison Levine from Canada 3-2 in her second of three group matches.

In her fourth appearance in the Paralympics in Tokyo, Lau will today be playing 24-year-old Samuel Andrejcik from Slovakia, who took the gold in the pairs event and a silver medal after losing to Leung in the 2016 Rio Paralympics.

However, teammate Wong Kwan-hang was unable to make the quarterfinals despite winning his final group stage match 5-3 against Japan's Shun Esaki.

In another class, Yeung Hiu-lam advanced to the quarterfinals after winning all three matches in the group stage of the BC2 individual event.

She won final group stage match over Portuguese Abilio Valente 4-3 and today faces Maciel Santos of Brazil, a gold medalist in London 2012, for a place in the semifinals.