A police officer has been shot dead in Makhachkala, the capital of Russia's North Caucasus republic of Dagestan.

A police spokesman told RIA Novosti that the attack took place late on Thursday and that the unknown assailant had opened fire after ringing the doorbell of the apartment where the officer lived.

The police officer died of his injuries on the way to hospital.

Five police officers were killed in a suicide bomb attack in Makhachkala on Wednesday.

Russia's North Caucasus republics, in particular Ingushetia, Dagestan and Chechnya, saw a sharp rise in militant activity in 2009.

MAKHACHKALA, January 8 (RIA Novosti)