The blast shattered windows and caused the ceiling to collapse. None of the injuries was serious.
BizVantage Beyond the news: when knowing counts.
Try the free, no-hassle 6 month trial!
Investigators say the bomb was left under a table at the fast food restaurant along Nevsky Prospekt, St. Petersburg's main street.
Authorities have not said if the attack was terrorist-related.
A car bombing of a Moscow McDonald's by Muslim extremists in 2002 killed one person and wounded seven.
Some information for this report was provided by UPI.