MOSCOW - An ethnic Russian woman, who was both wife and widow of Islamist militants, was named on Wednesday as the suicide bomber who killed a moderate Muslim cleric in the North Caucasus just as President Vladimir Putin was pleading for national unity.

Tuesday's assassination of Said Atsayev, 74, a prominent Sufi sheikh in the troubled province of Dagestan who had spoken out against violent Islam, heightened tensions which Putin, visiting another Muslim region, had been trying to calm.

Police said Aminat Kurbanova had posed as a pilgrim to the cleric's home and detonated an explosive belt packed with nails and ball bearings, killing Atsayev, herself and six others, including an 11-year-old boy visiting with his parents.

A security source said the woman, aged either 29 or 30, was born with the ethnic Russian family name Saprykina but converted to Islam and was married to an Islamist militant. Two previous husbands, also militants, had been killed, the source added.

Suicide missions by wives of fallen fighters, dubbed "Black Widows", has been a feature of guerrilla groups from Chechnya and neighboring Muslim regions in the past decade.

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