A suicide bomber blew up his car at a police checkpoint in Russia's restive North Caucasus region on Tuesday, killing a policeman and severely wounding three others, authorities said.
The pre-dawn attack destroyed the checkpoint on the internal border between the province of North Ossetia and Ingushetia. The region is plagued by near daily violence blamed on Islamist insurgents.
"A policeman stopped a car to conduct a check, and its driver detonated a bomb," the Russian Interior Ministry said on its website.
Televised footage showed shards of blue corrugated metal and other pieces of the small building scattered around the site with the snow-capped Caucasus Mountains in the background.
Moscow is struggling to extinguish the insurgency that stems from its two devastating wars against separatists in 1994-2000 in Chechnya, just east of Ingushetia and North Ossetia.
There is also lingering tension between mostly Christian North Ossetia and mostly Muslim Ingushetia two decades after a territorial dispute erupted into a brief war in 1992, but there was no indication the bombing was linked to that conflict.
President Vladimir Putin told security forces last week that they must ensure there are no attacks on major events Russia is to host in the coming years including the 2014 Winter Olympics in Sochi, near the North Caucasus.
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