Joshua, the WBA and IBF heavyweight champion, is now 19-0 with 19 knockouts, Censor.NET reports.
"I hope you enjoyed the fight. The best man won tonight. And it's an amazing event for boxing. Two gentleman fought each other and he was better today than I. It's really sad that I didn't make it tonight I was planning to do it but it didn't work. But all due respect to Anthony. Congratulations," Klitschko said.
Ringside judges Don Trella and Nelson Vazquez had Joshua ahead by scores of 96-93 and 95-93, respectively, at the time of the stoppage. Steve Weisfeld had Klitschko ahead 95-93.
27-year-old Joshua is a rising star who won gold for England at the 2012 London Olympics, made the third defense of his IBF title and picked up the vacant WBA belt in the process.