By Luke Furman

On Saturday night at the Bolshov Ice Dome in Adler, Russia - the punches were flying hard in the second semi-final fight of World Boxing Super Series (WBSS) cruiserweight tournament.

In a battle of undefeated world champions, Murat Gassiev (26-0, 19 KOs) pulled out a spectacular twelfth round knockout of Yunier Dorticos (21-1, 20 KOs) to unify the WBA, IBF world titles.

The fight was hard-fought by both men, but Gassiev closed the show by scoring three knockdowns in the final round to stop Dorticos.

The Cuban boxer started very fast and was pushing Gassiev back. Eventually the boxer who is nicknamed 'Iron' and is trained by veteran coach Abel Sanchez, began to land his rapid fire counter shots to the head, which slowly wore Dorticos down.

At the time of the stoppage, Gassiev was winning the fight on all three official scorecards - and the fourth scorecard, which is used in the event of a draw.

Gassiev will now advance this May to the WBSS championship final in Saudi Arabia, to fight WBO/WBC world champion Oleksandr Usyk (14-0, 11 KOs), winner of last Saturday's WBSS semi-final match against Mairis Briedis (23-1, 18 KOs).

The fight between Usyk and Briedis was highly competitive as well.

Usyk, an Olympic gold medal winner, was ringside for Gassiev's big victory and he was very impressed by the Russian boxer's performance.

After Gassiev won, Usyk entered the ring and the two boxers went face to face. There is a lot of respect between the two of them - and their contest sets up a Russia vs. Ukraine battle. 

Gassiev's promoter, Leon Margules of Warriors Boxing, believes his boxer will secure the knockout victory.

"We just saw a great fight. We saw how two warriors struggled with all of their heart. And today we could have seen the next best boxer in the world, a new superstar. How can you defeat this guy? In the final, he will knock Usyk out," said Margules to Nikolai Ryazantsev.

Luke Furman covers boxing for bokser.org.