MOSCOW — Two bomb attacks aimed at the police killed at least 12 people in the volatile North Caucasus region of Russia on Wednesday, according to the Russian prosecutor’s office, further heightening security concerns two days after deadly suicide bombings struck the Moscow subway.

Prime Minister Vladimir V. Putin said he did not rule out that Wednesday’s attacks in Dagestan, near the border with Chechnya, could have been organized by “the same group” behind the Moscow subway bombings. Dmitri A. Medvedev, Russia’s president, called the two sets of attacks “links of the same chain.”

“All this is the manifestation of the same terrorist activity which has recently started to resurface in the Caucasus,” Mr. Medvedev said.

Neither leader offered any evidence of a connection between the attacks in Moscow and Dagestan.

Law enforcement agencies throughout Russia have been on heightened alert since Monday, when two women set off explosions in the Moscow subway during the morning rush, killing 39 people in attacks that that shattered a sense that Muscovites were isolated from the continued terrorist violence in Russia’s south.

Although no one has claimed responsibility for any of the attacks, the North Caucasus region has been marked for particular scrutiny.

Russian officials have said the two suicide bombers on Monday likely came from Chechnya or a neighboring region in the North Caucasus.

For years Russia has been trying — unsuccessfully — to stamp out a lingering Muslim insurgency in the North Caucasus, including in Chechnya, where federal forces fought two bloody wars against Muslim separatists. Russian forces have killed several top militant leaders in recent months, and there has been speculation that a spate of recent attacks, including those in Moscow, were acts of revenge.

On Wednesday, the first of the bombs exploded in a parked car, killing two police officers who had pulled up beside it in their vehicle, according to a statement on the Web site of the prosecutor’s investigative wing.

As rescue workers and police officials gathered at the scene, a man wearing a police uniform walked up and set off his explosives, killing several more people, including the police chief of Kizlyar, the town where the attacks occurred. At least two dozen people were injured.

Channel 1 television showed what appeared to be cell phone video of police and firefighters wandering amid the wreckage of the first explosion when the second blast occurred, sending up a fireball and plume of smoke.

Such attacks, which are not uncommon in the region, are typically aimed at police and government officials, though civilians are often injured and killed. At least three of those killed in Wednesday’s attack were bystanders.

In the Moscow bombings, however, civilians appeared to be the prime targets. The bombers set off their explosives at two subway stations during the Monday-morning rush hour, the first such attacks in the capital in years.

Rashid G. Nurgaliyev, Russia’s interior minister, on Wednesday renewed a call for police to increase security in public places like theaters, schools and universities.

“These attacks show that terrorists can target anywhere,” he said.

Investigators have identified Daud Dzhabrailov, a local resident, as the bomber in the police uniform, the Interfax news agency reported.

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