At least 11 people were wounded on Saturday when the female bomber detonated explosives in the central square of Makhachkala, said police spokesman Vyacheslav Gasanov. He said the injured included police officers, civilians and two children.

The latest attack comes after twin car bombs in the city killed four people and injured dozens more on Monday.

Dagestan remains one of Russia's most violent regions. It has long been battling radical Islamist militants linked to an Islamic insurgency that spread through the mainly Muslim Caucasus region in the wake of two separatist wars in neighboring Chechnya.

Female suicide bombers – known in Russia as "black widows" – have behind at least two dozen suicide bombing in Russia since 2000. Their nickname stems from the fact that many are the widows or relatives of militants killed by security forces.

Dagestan is also home to the family of Dzhokhar and Tamerlan Tsarnaev who are suspected of carrying out last month's Boston marathon bombings. The brothers are ethnic Chechens who lived in Dagestan before moving to the United States. Three people were killed and dozens injured in the Boston attack.

ccp/mz (AFP, AP)