NEW YORK (AFP) - Unbeaten Kazakh star Gennady Golovkin stopped Australian Daniel Geale in three brutal rounds on Saturday to retain his World Boxing Association middleweight world title.

Golovkin sent Geale to the canvas in the second round with a barrage of blows.

In round three he responded to a hard right to the head from the Aussie challenger with his own punishing right to the nose, followed by a quick left that sent Geale down.

Geale, a former International Boxing Federation middleweight champion who fell to 30-3 with 16 knockouts, had no complaint when referee Michael Ortega called a halt at 2:47 of the round.

Golovkin, whose amateur resume included a silver medal at the 2004 Athens Olympics, improved to 30-0 with 27 knockouts.

Golovkin hasn't gone the distance since winning an eight-round decision in 2008 and said keeping his knockout streak alive was important.

"Yes, absolutely the knockout is very important, not just for me, not just for my team, but for everybody," he said. "This is big drama show."

Golovkin had fought twice before in Madison Square Garden's smaller Theatre, but he had never before fought in the fabled Manhattan venue's main arena.

After the bout, Golovkin said he wanted a unification bout with World Boxing Council champion Miguel Cotto - the Puerto Rican who is a longtime favourite of Garden fans.

Cotto became Puerto Rico's first four-division champion last month when he stopped Argentina's Sergio Martinez in nine rounds for the WBC middleweight belt in New York.

"I want a unification fight. I want who is the best in the middleweight division," Golovkin said, adding, when pressed: "Miguel Cotto - I respect him 100 per cent."