MOSCOW — Suicide bombers struck two stations in Moscow's crowded subway system less than an hour apart Monday morning, killing at least 37 people, injuring 73 and bringing Russia's seething northern Caucasus region to the Kremlin's doorstep.
Viktor Ilyukhin, the deputy chair of the security committee in State Duma, the lower house of Russia's parliament, said the attacks almost certainly were the result of deteriorating security conditions in Russia's mainly Muslim southern flank where a growing extremist insurgency has been spreading, largely below the world's radar screen, for the past couple of years.
"The terrorists are aiming at destabilization, their goal is to frighten the population," said Ilyukhin. "They also want to take revenge for the actions of the security forces against them, for the arrests and liquidations of their leaders," in the north Caucasus region, which includes the turbulent republics of Dagestan, Chechnya and Ingushetia, he said.
The first bomb, equivalent to about four kilograms (8.8 pounds) of TNT, exploded at the height of morning rush hour and killed at least 25 people inside a train that had just pulled into the Lubyanka station, which is a two-minute walk from Red Square and located beside the headquarters of Russia's FSB security service, the former KGB.
The second, smaller explosion, 45 minutes later on the same line, hit a train at Park Kultury, just across the street from a huge complex that houses the Kremlin news agency RIA-Novosti and the state-run English-language satellite network Russia Today.
An FSB spokesperson told journalists that, "According to preliminary information, both blasts were carried out by female suicide bombers" who brought explosives onto crowded metro cars and set them off in what appears to have been a carefully planned and coordinated series of attacks.
"There is no mistaking the symbolism of the targets; first the security services, and then the main center of state journalism," said Alexei Mukhin, the director of the independent Center for Political Information in Moscow, whose office is at Park Kultury. "The people who ordered these attacks were acting on a carefully thought-out plan."
President Dmitri Medvedev pledged to step up security in the Russian capital and to expand the security crackdown in the turbulent north Caucasus, which is the almost certain source of the threat.
"We will continue the operation against terrorists without hesitation and to the end," Medvedev said in televised remarks after the tragedy. "It is difficult to prevent such terrorist attacks and to provide security on transport," such as Moscow's sprawling and overcrowded metro system, he said.
"It is necessary to tighten what we do, to look at the problem on a national scale, not only relating to a certain populated area but on a national scale. Obviously, what we have done before is not enough," he added.
Security experts offered cautious praise for Russian authorities who appear to have avoided mass panic with a quick and competent response that contrasts sharply with clumsy reactions to previous terrorist strikes in downtown Moscow early in the past decade.
Police quickly cordoned off the areas, and thousands of shaken and frightened survivors were evacuated from the stations, which are among the deepest in the city, in an orderly fashion, and helicopters were brought into the paralyzed city center to extricate the wounded.
Violence in the north Caucasus has been spiking in recent weeks, including half a dozen bombings in Dagestan this month and two attacks by Ingush insurgents against local officials, most of which is scarcely reported, even in the Russian media.
Some experts suggest that the Moscow attacks might have been revenge for a security crackdown by Russian forces in the north Caucasus, which officials say has resulted in the killings of at least 35 leaders of extremist groups in Dagestan and Ingushetia this year.
"Things have been growing worse in the north Caucasus lately, but this is really the continuation of a threat we've been experiencing for the past 11 years," said Yulia Latynina, an investigative journalist who follows security issues. "Russia is the target of the international jihadist movement, but our state is less able to cope than many other countries."
Latynina said the female suicide bombers, who call themselves shakhidy, or martyrs, but have been dubbed "black widows" by Russian security forces, are an increasingly favorite tool of the insurgents. "By nationality, these shakhidy can be anything, even Russians," she said. "But by ideology they are Wahabi (Sunni Muslim extremists), and they are not a new threat to be seen in Moscow."
Moscow was the scene of a wave of terrorist attacks soon after Russian troops invaded the separatist republic of Chechnya for the second time a decade ago. A still unsolved wave of apartment bombings in the autumn of 1999 killed almost 300 people.
In subsequent years, more than 1,000 Russians died in terrorist strikes, including a siege of a downtown Moscow theater in 2002 and a series of bombings in Moscow markets, metro stations, and airliners.
However, after Russian troops pacified rebel Chechnya, the Kremlin declared victory, and a five-year hiatus in terrorist attacks against Russia's heartland appeared to confirm the efficacy of then-President Vladimir Putin's tough measures.
The bombing of a luxury train, crowded with officials, between Moscow and St. Petersburg last November, however, had many experts warning that terrorists might once again be eyeing civilian targets in Russia's heartland and developing new tactics.
"Bandit underground activity is still on, so they wanted to prove once more that they still exist and they are active," said Sergei Goncharov, the head of a special forces veterans' group. "This surely comes from the north Caucasus, which is a wound for Russia that cannot be healed."
(Weir is a Christian Science Monitor correspondent.)