"The woman was found unconscious in Udelny park and cannot answer questions yet," the source said, adding that the 32-year-old woman had been taken to hospital in a critical condition.
Hospital officials said the victim had been admitted in the morning and diagnosed with open brain injury, and fractures to the nose and skull base.
The victim has already undergone surgery. "The woman is now in intensive care, and is in a serious condition," the source said.
An inquiry has been opened into the incident in western St. Petersburg, the latest of a series of attacks on ethnic minorities in the city in recent years.
The woman's compatriot, a nine-year-old Tajik girl, died of stab wounds in St. Petersburg in February 2004 after being attacked along with her father and 11-year-old cousin by a group of young men.
The main teenaged defendant in the case was cleared of race-hate murder but convicted of robbery and hooliganism, just like another six defendants. In all, seven of eight arrested attackers were sentenced to 1.5 to 5.5 years in jail, and one was cleared of all charges. The investigation established that 11 people had been implicated in the attack.
