MOSCOW—Russians named in an unverified dossier on President-elect Donald Trump reacted with incredulity to allegations they were tied to Kremlin-led efforts to interfere with the U.S. elections.

The dossier contains claims that Russian officials have compromising evidence about Mr. Trump’s behavior that could be used to blackmail him, and that the Kremlin colluded with members of Mr. Trump’s team to help get him elected. Mr. Trump and the Russian government have both dismissed the claims.

Aleksej Gubarev, the chief executive of XBT Holding, a Luxembourg-based web-hosting company, was named in the dossier as a “hacking expert” who had been involved in efforts to “transmit viruses, plant bugs, steal data and conduct ‘altering operations’ ” that targeted Democratic Party leadership. The dossier said those efforts had Kremlin sanction at the highest level, and involved Russian spy agencies including the Federal Security Service, or FSB.

“Imagine how surprised I was,” said Mr. Gubarev, referred to in the dossier as Alexei Gubarov. “I bet the FSB was also surprised to see my name in this report.”