Sergey Kovalev retained his World Boxing Organization title by beating fellow Russian and heavy underdog Igor Mikhalkin when the light heavyweight fight was stopped by the ring doctor in the seventh round.

Kovalev earned his second-straight knockout since losing his three titles to Andre Ward as he destroyed the challenger with ease on Saturday night at Madison Square Garden arena in New York.

“I am back,” said Kovalev, who trains out of Los Angeles. “He looked easy but he was a good boxer and had good stamina.”

The referee stepped in and halted the onslaught and waved over the ring doctor who called it off with 35 seconds left in the final round. At the time, the 32-year-old Mikhalkin was bleeding heavily from a cut under his right eye and another on the bridge of his nose.

Kovalev improved to 32-2-1 with 28 knockouts with the first defence of the title he won three months ago by beating another little known opponent in Vyacheslav Shabranskyy.

The German-based Mikhalkin dropped to 21-2 as the southpaw was facing the first name opponent of his career. The loss ended a string of 11 straight wins going back to his decision loss in 2010 to Aleksy Kuziemski.

Kovalev is working his way back after losing all his titles in one go 16 months ago.

He lost his three light heavyweight title belts to Ward by controversial decision in November 2016, and then lost to Ward again in the immediate rematch, this time by eighth-round knockout last June.