Dagestan experiences almost daily bombings that officials blame on fighters with links to Chechnya [AFP]

A high-level security official has been killed in a drive-by shooting outside in the capital city of Dagestan, in Russia's North Caucasus region, RIA Novosti, the Russian state news agency, reports.

Mohammed Murtazaliev, the deputy head of the federal penitentiary service of Dagestan, was shot dead and "his daughter, nephew and driver also died when the car caught fire following an ambush by gunmen on Friday morning in the village of Samandar, on the outskirts of Makhachkala", RIA Novosti said.

The Investigative Committee, Russia's highest investigative body, said in a statement that the four victims were driving in a car when they were sprayed by automatic weapon fire from another vehicle.

The mainly Muslim region of Dagestan experiences almost daily shootings and bombings that officials blame on local criminals and fighters with links to Chechnya.

Three car bombs exploded in Makhachkala over a two-day period, killing at least six people and injuring more than 61 others.

Two car bombs exploded on Thursday within metres of each other near Dagestan's interior ministry in Makhachkala,  killing one police officer and a civilian.

The blasts followed an explosion in the same city late on Wednesday which killed at least four people and injured five passers-by.

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.

The Kremlin fought two wars against separatists in Chechnya in the 1990s, and the violence has since spread into the nearby regions of Dagestan and Ingushetia.