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MOSCOW, Dec 17 (Reuters) - An unknown attacker stabbed and killed the mayor of a town in northwest Russia, news agencies quoted a security service source as saying on Wednesday.

Motives for the attack on Tuesday evening on the mayor of Kandalaksha, Nina Varlamova, are unclear, the source said.

"An unknown person ran towards the mayor, who was leaving a house, stabbed her in the neck and fled," the source said.

Varlamova became mayor in 2007 after the previous mayor was jailed for bribery, news agencies said.

Kandalaksha is a town of about 50,000 people in the Arctic circle about 300 kms (185 miles) south of Murmansk, the regional capital. (Writing by James Kilner; Editing by Janet Lawrence)

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