Niyazymbetov got the better of a close opening round, but the Russian battled back to level matters at 8-8 in the second.
The Kazakh looked like the man producing the better quality, but Mekhontcev used his jab well to keep the scoreboard ticking over.
It was very much nip and tuck as the clock ticked down. The Russian found the mark with a decent right hand, but Niyazymbetov replied with a decent left.
An evenly-matched contest came to a close with the judges scoring the bout evenly.
No winner could be found on countback, but the judges sided with Mekhontcev on a vote.