A suicide bomber has blown herself up in the capital of the troubled southern republic of Dagestan, Makhachkala. Fifteen people including five policemen were wounded.
The bombing occurred near an interior ministry building just before midday on Saturday.
Officials said the force of the blast was equivalent to around 500g of TNT.
The BBC reports Russia has seen a number of attacks in recent years by female suicide bombers, known as black widows.
They are often related to fighters killed during a separatist campaign against Russia, particularly in the North Caucasus, where Dagestan borders Chechnya.
Russian news agencies reported the bomber has been identified as Madina Aliyeva, 25, a widow.
Interfax news agency was told her first husband was killed in 2009 and her second husband in 2012.
Four people were killed and many more wounded in two car bomb explosions in Makhachkala on Monday.