The Serbia international is alleged to have entered into a row with a supporter carrying an Albania flag during Manchester City's 3-1 win at St James' Park on Saturday afternoon
A statement released confirmed that the incident took place during the game, were it is alleged Kolarov confronted a fan carrying an Albania flag as he warmed up.
Relations between Albania and Kolarov's native Serbia have been tense for a number of years, with flashpoints between the two nations during the Yugoslav wars in the early 90s. The Serbian government were also unhappy with Albania backing Kosovo as an independent state in 2008.
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A spokesman said: "Northumbria Police has received a report of racist language having been used at the St James' Park stadium during the Newcastle United v Manchester City match today.
"Northumbria Police takes such allegations extremely seriously and enquiries are ongoing into the incident."
City won the game 3-1 thanks to goals from Sergio Aguero, Javi Garcia and Yaya Toure, while Demba Ba netted the hosts' solitary strike.