MACAU (AP) — Russia's Evgeny Gradovich retained the IBF featherweight title after Australia's Billy Dib quit in the ninth round Sunday on the undercard of the Manny Pacquiao-Brandon Rios fight at The Venetian casino in Macau.

In a rematch of their bout in March, Gradovich put Dib down in the sixth round and staggered him with a left hook in the eighth. Further punishment in the ninth prompted Dib's corner to ask the referee to stop the fight.

Mexican heavyweight Andy Ruiz Jr. extended his unbeaten record when American opponent Tor Hamer quit after three rounds despite leading on two of the three judges' scorecards. Ruiz retained his WBO intercontinental heavyweight belt and added the NABF title.

Zou Shiming, China's two-time Olympic gold medalist, improved his professional record to 3-0-0 with a unanimous points decision in his six-round flyweight bout against Mexico's Juan Toscano.

After an even opening couple of rounds, Zou poured on the pressure in the third round, opening a cut under the Mexican's right eye, and sustained his dominance from then on to claim an impressive victory.

Highly touted lightweight Felix Verdejo of Puerto Rico improved his record to 8-0-0 with a unanimous points decision over Petchsamuthr Duanaaymukdahan, exhibiting too much hand speed and movement for the resilient Thai.

The other bouts saw Filipino lightweight Harmonito Dela Torre knock out Indonesia's Jason Butar Butar in the third round; China's Ik Yang take a split decision over Indonesia's Hero Tito; local Macao fighter Kuok Kun Ng take a unanimous decision over China's Zeng YouJie; Hong Kong's Rex Tso stop Thailand's Susu Sithjadaeng in the first round; and Filipino Dan Nazareno Jr. beat Liam Vaughan when the Englishman's corner stopped the fight in the second round.