A deal to free Alexei Navalny was "in progress and in the final stages" before he died in prison just over a week ago, his team said, AFP reported.
The 47-year-old Kremlin critic died on February 16 after spending more than three years behind bars, sparking outrage and condemnation from Western leaders and his supporters.
Russian President Vladimir Putin "was offered to exchange FSB officer and assassin Vadim Krasikov, who is serving a murder sentence in Berlin, for two American citizens and Alexei Navalny," ally Maria Pevchikh said.
"I had received confirmation that negotiations are underway and are at the final stage" after two years of talks between Moscow, Washington, and Berlin, she added.
"It was assumed that Navalny would be released in the coming days," she added.
Asked about the allegations during a regular briefing, a German government spokeswoman declined to comment.
Krasikov is serving a life sentence in Germany for the 2019 killing of former separatist commander Zelimkhan Khangoshvili in a Berlin park, which German authorities say was ordered by Russian intelligence services.
Washington accuses Moscow of arresting American citizens on baseless charges to use them as bargaining chips to secure the release of Russians convicted abroad.
Among the American citizens detained in Russia are former US Marine Paul Whelan and Wall Street Journal reporter Evan Gershkovich, both accused of espionage. /BGNES
