They were promptly stopped. ''Police officers spotted them, confiscated their passports and handed them over to a police captain responsible for antiterrorism operations to examine their belongings and check these people for their potential role in terrorist attacks,'' Mr. Ustinov said. ''The captain let them go without any checks, and they started to try to obtain tickets in the same buildings.''
Next, he said, the women received help from Armen Arutyunov, a man apparently acting as a ticket scalper, who took an amount in rubles worth roughly $68 from one woman and $103 from the other.
Two minutes before the end of passenger registration for Flight 1047, Mr. Arutyunov handed 1,000 rubles, worth $34, and a ticket for a flight the next day in the name of Ms. Dzhbirkhanova to the Sibir Airlines official; the official wrote on the ticket ''Admit on Flight 1047'' and let Ms. Dzhbirkhanova board the jet, Mr. Ustinov said.
At about 11 p.m., as the plane was en route to Russia's Black Sea port of Sochi, it exploded, scattering its wreckage and cargo for miles. The second aircraft, carrying Ms. Nagayeva, exploded at the same time while flying another route. Everyone on both planes died. Both the Sibir official and Mr. Arutyunov have been arrested, Mr. Ustinov said.
In the portion of his remarks available thus far, Mr. Ustinov made no suggestion that the airline official who accepted the cash payment was aware that Ms. Dzhbirkhanova planned to commit a terrorist act. He also did not address how the women managed to pass through luggage checks -- a procedure separate from purchasing a ticket. A spokesman for Domodedovo International Airport, which is responsible for luggage checks, declined to comment.
Ilya Novakhatsky, a Sibir Airlines spokesman, suggested the case against the official who accepted the $34 was overblown, and was drawing attention away from another element of the case. ''It is the work of airline representatives to help passengers, including rebooking them,'' he said. ''Inspection is the work of airport security. It is paid for by the airlines, but carried out by the airport. Employees of airlines are not authorized to inspect luggage.''
Mr. Ustinov's remarks also did not explain how Ms. Nagayeva boarded the plane the authorities say she later destroyed. Nor did they explain the roles or whereabouts of the two Chechens he said accompanied the women at the airport, or the rationale of the police captain who allowed the women to go free after they were briefly detained.
Russia employs a vast domestic security apparatus -- police of all sorts are a visible element of public life here -- and it has deployed its army internally in the Chechen war in an effort not only to defeat Chechnya's separatists, but to contain the flow of terrorists from the war zone. But military analysts have said that low professionalism and corruption render them much less effective than their numbers and visibility might suggest, and Mr. Ustinov's announcement offered insight into just how porous the security can be.
Ms. Panfilova said she worried that even the news of the role of a bribe in the terrorist act would have little effect on corruption here, because among Russians bribes are an ingrained part of life. A concealed bomb, she said, would remain easy to smuggle.
''Go tomorrow to a train station and say to the conductor, 'I have a little parcel, you know, they are school books for my nephew and my nephew will pick them up at the next city,''' she said. Offer him money, she added, and ''I'll bet you 8 out of 10 of the conductors will take them.''