MAKHACHKALA, Russia— A suicide bomber blew up an explosives-packed car at a police station in Russia's troubled North Caucasus on Wednesday, killing at least six officers and wounding 16, police said.

But the officers who died took action to prevent far greater devastation at the traffic police station on the outskirts of Makhachkala, the capital of Dagestan, where the bombing took place as 150 officers lined up outside for roll call, city police chief Col. Shamil Guseinov said.

The bomber detonated the explosives at the station gate after police stopped him from driving through, Guseinov said. Those killed were at the gate, including three officers in a police jeep that blocked the attacker's path, he said.

Police estimated that 50 to 200 kilograms (110 to 440 pounds) of TNT was packed into the Niva, a small Russian-made SUV.

The blast damaged the police station and blew out the windows of a nearby building. Buckshot from the bomb was scattered across the area.

Guseinov said police had received information about a planned attack and had moved the daily roll call well inside the station's territory, 200 meters (yards) from the gate.

President Dmitry Medvedev immediately ordered the interior minister, who oversees Russia's police, to step up security in Dagestan and provide assistance to the families of the officers who died.

A similar bombing in a neighboring republic in August killed 24 people and injured more than 200. In that attack, a man succeeded in crashing a bomb-laden van through the gates of the police station in Nazran, Ingushetia. The explosion left a bus-sized crater in what was left of the station.

Dagestan and Ingushetia border Chechnya, where Russian troops have fought two full-scale wars against separatist rebels in the past 15 years.

All three predominantly Muslim republics in the North Caucasus have seen a sharp rise in violence in the past year, with many of the nearly daily attacks targeting police and other officials.

In the most recent violence in Chechnya, four police troops were injured in two separate attacks on Tuesday. In both cases, an explosive device blew up as the troops walked along a village road or wooded path, police spokesman Magomed Deniyev said.

The violence sweeping the impoverished southern region has been described as a civil war between Kremlin-supported administrations and Islamic militants. Widespread abuses against civilians by police, including abductions, torture and killings, have helped to swell the ranks of the militants. (AP)