Russian police says attackers set fire to a Muslim prayer house in a southern Russian city earlier rocked by a suicide bombing.

Volgograd police said Tuesday someone threw Molotov cocktails at the building late Monday night, but the custodian managed to put it out. Houses with rooms set aside for Muslim prayer are common in southern Russia.

A female suicide bomber blew herself up on a city bus on Monday, killing six people and injuring about 30. She is believed to be the wife of an Islamic militant.

The suspected bomber was from the North Caucasus, a region in southern Russia where an Islamic insurgency has been simmering for more than a decade following two separatist wars in Chechnya.