MOSCOW — A blast that destroyed much of a nine-story Moscow apartment building Thursday, killing at least 47 people and burying dozens more under a pile of rubble, was caused by a bomb and is being investigated as a terrorist act that may be linked to Russia's war with Islamic separatists, authorities said.
The explosion, which officials said was caused by a device on a lower floor, fueled widespread fear that the war against Islamic insurgents in the southern republic of Dagestan is spreading to Moscow.
The blast, which officials initially suspected was caused by a natural gas leak, was the third to kill Russian civilians in 10 days. On Saturday, a car bomb demolished an apartment building that housed Russian military families in the Dagestani city of Buynaksk, killing at least 64 people. On Aug. 31, a bomb rocked a popular Moscow shopping mall next to the Kremlin, killing one and injuring 40.
After touring the latest disaster scene Thursday, Moscow Mayor Yuri M. Luzhkov tied the carnage to the conflict in Dagestan and said the blast was caused by hexogen, a plastic explosive often used in military operations.
"Now it is possible to claim with the highest degree of certainty that this was an act of sabotage, this was a terrorist act," Luzhkov said. "The repercussions of the war in Dagestan are felt in the first place in the capital, as the most sensitive place in the Russian state."
The nighttime blast was so severe that a large section in the middle of the building collapsed, leaving little hope of finding survivors. Rescuers using cranes worked all day and into the night, but a fire deep in the ruins further reduced the chances of finding anyone alive.
The explosion comes on the heels of a new offensive launched by rebels based in Chechnya, who crossed the border into Dagestan during the weekend and seized several villages in their quest to expand Islamic control in the turbulent Caucasus region.
In a telephone conversation Wednesday with FBI Director Louis J. Freeh, Interior Minister Vladimir B. Rushailo said Russian officials believe that Saudi Arabian militant Osama bin Laden is financing and inspiring the rebels' invasion of Dagestan.
The United States has accused Bin Laden of masterminding the 1998 bombings of U.S. embassies in Kenya and Tanzania. Rushailo said he had information that Bin Laden had sent millions of dollars to Chechen warlords who are leading the Dagestan campaign.
On Tuesday, Russian President Boris N. Yeltsin lashed out publicly at his generals for their inability to halt the rebels and for their "sloppiness" in not preventing the Buynaksk bombing inside a military compound.
Some opposition politicians have expressed concern that the war and bombings could give Yeltsin a pretext to declare a state of emergency, cancel presidential elections set for next summer and continue to rule. The Kremlin insists that Yeltsin plans to step down next year on schedule and hand over power to an elected successor.
The conflict in Dagestan has parallels to Russia's war in Chechnya, which began as a brief operation to quell separatist rebels but turned into a 20-month war that claimed as many as 80,000 lives. Since the war ended in 1996, Chechnya has become a lawless, autonomous state where warlords control much of the territory and kidnappings are common.
Early last month, rebels led by warlord Shamil Basayev entered Dagestan but withdrew two weeks later in the face of heavy fire from Russian troops. While the Russian commanders were celebrating, as many as 2,000 insurgents crossed the border again last weekend, seized new villages and dug in.
On Thursday, Russia said an Su-25 fighter plane crashed because of mechanical problems while carrying out air raids against the rebels. Chechen officials charged that Russia had bombed villages on their side of the border, killing 128 people.
In Moscow, no organization claimed responsibility for Thursday's blast, but an anonymous caller to the Interfax news agency said both apartment bombings over the past week were "our response to the bombing of villages in Chechnya and Dagestan."
German Deutsche Welle radio reported that a caller had warned its Moscow correspondent Monday that there would be "three explosions in Moscow" as "an act of anger in the wake of the Russian army's bombing of Chechen villages."
The explosion shortly after midnight demolished 72 apartments in the 216-unit building, which is part of a large residential complex on the southeastern edge of the city. The blast damaged more than a dozen nearby buildings.
Luzhkov said 153 people had been pulled from the rubble; 77 were taken to hospitals. Estimates of the number still trapped in the ruins ranged as high as 100.
"The very fact that a terrorist can blow up half a large apartment building right in the capital of Russia strikes fear in many hearts in this country," said Dmitri V. Trenin, a national security expert with the Carnegie Moscow Center. "No one in Russia today believes that the authorities will be able to protect the people from terrorism."