|Blasts are a near-daily event in Dagestan, where fighters are seeking to carve out a separatist Islamic state [Reuters]
At least six people have been killed and more than 61 others injured after three car bombs exploded in the capital of the predominantly Muslim Dagestan region in Russia's North Caucasus.
The first car detonated in Makhachkala on Wednesday at 7:30pm (15:30 GMT), killing at least four people and injuring five passers-by, according to an interior ministry source, speaking on condition of anonymity.
Two more car bombs exploded within metres of each other after midnight, killing one police officer and a civilian, the source told the reporters.
The blasts occurred about 500 metres from the offices of Dagestan's interior ministry, a representative of Makhachkala police said.
"A police lieutenant died, and about 60 people went to the hospital," he said.
"The first blast was to attract attention, and the second was directed [at people] as the area was being closed off."
The second bomb was planted in a car and the blast was equivalent to about 35kg of TNT, he said.
The debris of two cars lay crumpled on a main thoroughfare where blood was pooled near a row of shattered and blackened stores and cafes, state TV showed.
In another region of Dagestan, several people assaulted a local police chief in the town of Buinaksk on Thursday morning, killing his two bodyguards.
"They stopped his car as he was going to work and opened fire from machine guns," a police representative in Buinaksk, which lies about 30km southwest of Makhachkala, said. The chief, a police colonel, was unharmed.
The Caspian Sea region of Dagestan experiences almost daily shootings and bombings that officials blame on local criminals and Muslim fighters with links to Chechnya.
The fighters are battling for a separate Islamic state in the mainly Muslim North Caucasus along Russia's southern frontier.
Dmitry Medvedev, the Russian president, has named the unrest there the country's chief security threat in the year before the March 2012 presidential election.
The fighters took responsibility for a suicide bombing at Moscow's Domodedovo airport that killed 37 people in January, as well as twin metro attacks last year that killed 40 people.