ST. PETERSBURG, Russia -- A match between Zenit St. Petersburg and Dynamo Moscow on Sunday was abandoned after Zenit fans invaded the pitch and one of them attacked an opposition player.
Dynamo led 4-2 in St. Petersburg when the pitch invasion began in the 87th minute, a result that would hit Zenit's hopes of winning the Russian Premier League title if it stands.
Broadcasts showed one of the fans running up to Dynamo defender Vladimir Granat and punching him in the head from behind.
Granat has a head injury, Dynamo's sporting director Guram Adzhoev was quoted as saying in local media. Granat has four caps for Russia and is considered a contender to play at the World Cup next month.
Zenit expressed "deep regret'' at the behavior of its fans and said it was working with police to identify Granat's attacker.
"The club understands that fans have the right to be disappointed and displeased with the team's play,'' Zenit said in a statement. "But hooliganism and disorder are not acceptable in any case.''
Yuri Chebotaryov, the Russian Football Union delegate assigned to the game, was quoted by the Sport Express newspaper as saying he believed the unrest had been "planned'' by Zenit fans. "The fans were ready to go onto the pitch, regardless of how events unfolded,'' he said.
It remains unclear whether the score at the time the game was abandoned will be considered the final result. The Russian Football Union's disciplinary committee, which rules on such matters, meets each Wednesday.
Earlier, the game was briefly delayed when Zenit fans let off flares and smoke bombs, severely reducing visibility at the Petrovsky stadium.
For now, Zenit has slipped to second in the league standings behind CSKA Moscow and could fall to third later Sunday.
In 2012, a match between Zenit and Dynamo was abandoned when a flare thrown from the Zenit fan sector injured Dynamo goalkeeper Anton Shunin.
Sunday's pitch invasion is the first major case of unrest involving Zenit fans this season, although other top Russian clubs have seen disorder, four years before the country hosts the World Cup.
In October, Spartak Moscow fans clashed with police during a cup game at which a swastika flag was also displayed. Around 40 fans were reportedly arrested.
Defending Russian champion CSKA was ordered to play its next European game behind closed doors in February after UEFA charged the club over racist behavior by its fans in the Champions League for the second time this season.