MOSCOW (AP) — A Russian Premier League referee has been cleared of racially abusing Zenit St. Petersburg striker Hulk.

The Brazil international accused Alexei Matyunin of racially insulting him in English during Zenit's 1-0 defeat to Mordovia Saransk in November, in a case which highlighted Russia's struggles with football racism.

"A serious personal conflict took place" between Hulk and Matyunin, Russian Football Union ethics committee head Vladimir Lukin ruled on Friday, but there was no "direct proof" of racist behavior by the referee.

Matyunin denied the accusation, and there were no other witnesses.

"It is not possible to establish what exactly the match referee said to Hulk," Lukin said in a statement, telling Matyunin that in future he should "strictly keep to the status of an official, not breach the principles of fair play, and behave respectfully to the competition participants."

Hulk was told that players should not have "any discussions" with referees.

Matyunin was previously banned for a year in 2011 over allegations he used a racial slur when speaking to a player from Russia's North Caucasus region during a game. That ruling was later overturned on appeal.

Friday's decision follows numerous racism-related incidents in Russian football in recent months.

Hulk was abused with monkey chants by Spartak Moscow fans during a league game in September, for which Spartak fans were banned from attending the club's following away game.

Two African players, Dynamo Moscow defender Chris Samba and FC Rostov midfielder Guelor Kaku Kanga, received bans this season for making offensive gestures at fans who racially abused them during Russian Premier League matches.

Russian champion CSKA Moscow was forced to play all three of its home Champions League group stage games behind closed doors as punishment from UEFA for racist behavior and violence by its supporters.