Moscow Muscovites fear Tuesday's deadly rush-hour explosion might signal the start of another terror campaign, like the series of bombings a year ago that killed 300 people and sent the capital city of 10 million people into a near panic.
Several Russian officials and independent analysts blamed Chechen terrorists for Tuesday evening's blast in a crowded underground passageway in downtown Moscow, but Russian President Vladimir Putin said it would be wrong to "brand a whole people" for the act.
At the same time, however, Putin said Russia has "allowed an entire enclave of terrorism inside this country," an obvious reference to the breakaway republic of Chechnya, where rebels are fighting for independence from Russia. "The state will not let them go unpunished," he said in a Kremlin meeting that was aired on nationwide TV.
Experts said renewed terrorism in Russia could prompt Putin to abandon efforts to negotiate a settlement in Chechnya and instead escalate Moscow's 11-month-old effort to crush the separatists.
Recent polls show that more Russians are growing weary of the war as Russian casualties mount. On Tuesday, a remote-controlled bomb killed two Russian policemen in Chechnya, and at least nine Russian checkpoints came under rebel attack.
Authorities said the Moscow blast Tuesday under Pushkin Square, less than a mile from the Kremlin, killed seven people and injured 93. Russian news agencies earlier had reported that an eighth victim had died, but the Health Ministry said the report was a mistake.
Nikolai Patrushev, head of the Federal Security Service, or FSB, the main successor agency of the KGB, called the explosion a "terrorist act."
Without giving details, he said investigators disrupted 11 similar attacks last month in the Russian republics of Chechnya and Dagestan and the cities of Volgograd, Nishny Novgorod and Tula.
"International terrorists and illegal armed formations are still active in Chechnya," he said, echoing the Kremlin's claim that militant Islamic groups are aiding the Chechens. "They have opted for the tactics of subversive and terrorist acts."
In the central Russia city of Saratov, FSB agents arrested three Chechens suspected of plotting an attack similar to that in Moscow, the Interfax news agency reported. Investigators confiscated 7 ounces of plastic explosive, an electric primer, a portable army radio and a Makarov pistol.
Interfax also reported that a bag containing TNT was found Wednesday in a lost-luggage section of Moscow's Kazansky railway station.
Police inspected cars and trucks entering the city Wednesday and increased patrols of subway terminals. Earlier in the day they questioned and then cleared two men who they said were from the north Caucasus region, which includes Chechnya. People across the city volunteered for sentry duty at their apartment buildings.
"I was badly shaken, and, of course, I mourn those who were killed," said Nelya Burnova, a teacher and free-lance journalist. "Unfortunately, I think there will be other attacks. We all have to pull ourselves together and be very attentive."
Some Russians said in sidewalk interviews that it would be wrong to blame Chechens without adequate evidence. Chechen President Aslan Maskhadov has denied Chechen involvement in the blast.
Two widely circulated theories about the explosion echoed those from last year's attacks that the instigators could either be Chechen terrorists eager to sow destruction in the Russian heartland or security forces eager to stoke Russian hatred of Chechens and strengthen Putin's hand in the conflict.