Russian authorities and witnesses say a suspected bomb exploded Sunday in a McDonald's restaurant on St. Petersburg's main street, injuring six people.

The blast shattered windows and caused part of the restaurant's ceiling to cave in. None of the injuries are said to be serious.

The blast occurred along Nevsky Prospekt. Police closed down part of St. Petersburg's main street while they carried it their investigation.

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 AFP, AP and Reuters.