MOSCOW — The huge banner was unfurled on Friday morning outside one of Moscow’s biggest bookstores, Dom Knigi, a grand emporium of the written word on Novii Arbat Street across from a Citibank, a Baskin-Robbins and a Dunkin’ Donuts, and down the block from a big movie theater where the main feature at the moment is “Captain America: The Winter Soldier.”

“Fifth Column,” the banner declared. “Strangers Among Us.” It showed black-and-white portraits of three of Russia’s better-known political opposition figures and two Soviet-era dissident rock musicians, along with two evil-looking space aliens, one carrying a briefcase marked with the white ribbon that has been the symbol of political protests against President Vladimir V. Putin and the Russian government.

From the moment that Russia’s invasion and annexation of Crimea cast a new, bitter chill over relations with the West, a sinister jingoistic vibe has pervaded this unsettled capital — stirred up by state-controlled television and Mr. Putin himself.

“Some Western politicians are already threatening us not just with sanctions but also the prospect of increasingly serious problems on the domestic front,” the president said in his speech announcing plans to absorb Crimea into the Russian Federation. “I would like to know what they have in mind exactly: action by a fifth column, this disparate bunch of ‘national traitors,’ or are they hoping to put us in a worsening social and economic situation so as to provoke public discontent?”