About 50 African and Asian students marched through Russia's second largest city on Thursday to protest at police refusal to treat the killing of a Congolese national as a racial attack.
A 29-year-old student Roland Epassak, died Wednesday, five days after being attacked.
City prosecution spokeswoman Yelena Ordynskaya said that prosecutors were not treating the crime as racially motivated and suggested it could be an act of hooliganism.
St. Petersburg criminal police chief Vladislav Piotrovsky said Epassak and two others had been drinking alcohol in their apartment and had then gone outside, where they encountered people belonging to "the most scandalous contingent" in the neighborhood.
Andrew Suberu, the head of St. Petersburg's Nigerian community, who took part in Thursday's march, called the police statement "nonsense."
The attack was the latest of a growing number of attacks in Russian cities on dark-skinned foreigners and immigrants from Central Asia and the Caucasus region in recent years, reports the AP.