When Mr. Putin spoke, “it was a rocket with a nuclear engine,” Yulia Latinina, a columnist for Novaya Gazeta, an opposition newspaper, wrote. “And when it blows up it is a liquid unit with isotopic sources.”
Boris L. Vishnevsky, a member of the St. Petersburg City Council, said dozens of people have called, asking for clarification about radiation risks.
“People need reliable information,” Mr. Vishnevsky said. “And if the authorities think there is no danger, and nothing needs to be done, let them announce this formally so people don’t worry.”
For Mr. Kotsyubinsky, the St. Petersburg resident who said he was worried about radiation, the statement released in the wee hours, the contradictory accounts and the silence of senior officials have conjured dark memories of Chernobyl.
As a 21-year-old college student, he said, he was ordered to march in a May Day parade in 1986. The Soviet authorities, wary of revealing that a nuclear accident had occurred just days earlier, did not cancel parades around the country in which millions of children participated.
In Ukraine, where Chernobyl is, wind bearing radioactive dust swirled around the clueless children. In northern Russia, a cancerous rain fell. With these memories still fresh, Russia adopted a Constitution in 1993 that prohibits classifying information about public health risks.
“They made us go to these demonstrations,” Mr. Kotsyubinsky said. “We didn’t know. We wound up under the rain. It wasn’t lethal, but it was radioactive. That shouldn’t happen in a society where the government answers to the people.”