(CNN) -- English football's battle against racism took an unexpected turn on Saturday as police announced an investigation into an alleged altercation between a Serbian player and an opposition fan at a Premier League match.
Manchester City's Aleksandar Kolarov reportedly clashed with a supporter who was waving an Albanian flag during the game at Newcastle.
"Northumbria Police has received a report of racist language having been used at the St James' Park stadium during the Newcastle United vs. Manchester City match today," the police said in a statement.
"Northumbria Police takes such allegations extremely seriously and enquiries are ongoing into the incident."
Serbia international Kolarov was born in the capital Belgrade. His country has long been in dispute with Albania over the Kosovo region, where war broke out in 1998.
The defender was warming up on the sidelines before coming on as a first-half substitute when the argument occurred, according to the UK Press Association.
Neither club was prepared to comment on Saturday, the Press Association reported. Manchester City did not immediately respond to CNN's request for a statement.
It was the second match in a row involving City where non-footballing controversy has overshadowed on-pitch action.
Last weekend's Manchester derby was marred by a coin attack on United player Rio Ferdinand, a pitch invasion by a supporter and arrests of other fans for alleged racist abuse.
The Kolarov incident came two days after Serbia was fined $105,000 by UEFA following complaints of racial abuse from England players during an Under-21 match in October.
It is the latest in a series of racism controversies going back more than a year, involving top players such as Chelsea's former England captain John Terry and Liverpool striker Luis Suarez. Referee Mark Clattenburg was accused of racially abusing a Chelsea player in October before being cleared.
City bounced back from Sunday's 3-2 home defeat to beat Newcastle 3-1 and keep the pressure on leading club Manchester United.
Striker Sergio Aguero and midfielder Javi Garcia put City 2-0 ahead before Demba Ba reduced the deficit with his 11th league goal this season, then Yaya Toure wrapped it up from Kolarov's cross.
Kolarov did not complete the match, being substituted with 18 minutes to play.
Manchester United stayed six points clear of Roberto Mancini's second-placed defending champions, beating Sunderland 3-1.
Robin van Persie returned to the top of the scoring charts with his 12th EPL goal and 15th overall since signing from Arsenal in August, while midfielder Tom Cleverley made it 2-0 in the 19th minute and Wayne Rooney followed up his double against City with his seventh in the league in the second half.
Struggling Sunderland rallied with a 72nd-minute goal from former United striker Frazier Campbell, but Alex Ferguson's team held on to guarantee they will be top of the table come Christmas -- and the title has gone to the team in that position for the past three seasons.
It was an eventful day in the Premier League as Queens Park Rangers moved off the bottom with the club's first win in 17 games, winning 2-1 at home to London rivals Fulham to extend new manager Harry Redknapp's unbeaten run to four matches.
Both goals came from Morocco midfielder Adel Taarabt, who was sold to QPR by Redknapp in 2010 when he was boss of Tottenham.
Fourth-placed Everton drew 1-1 at Stoke, but may lose eight-goal midfielder Marouane Fellaini to suspension if the Belgian is punished for a headbutt that the match official did not see.
"We will take the punishment if it is given for it," Everton manager David Moyes said.
"I have told him in the dressing room that it is not acceptable -- I won't accept it as a manager that he does that."
Norwich moved up to seventh with a 2-1 win at home to third-bottom Wigan.
Aston Villa moved away from the relegation zone with a 3-1 win at Liverpool as Belgium international Christian Benteke scored twice, with the other goal coming from fellow young striker Andreas Weimann.
Captain Steven Gerrard scored a late consolation as Liverpool's three-match winning run ended, leaving Brendan Rogers' team 12th -- five points behind Merseyside rivals Everton.