Paypal has blocked a Russian account that was intended to fund large-scale publication of the report opposition leader Boris Netmsov was working on when he was murdered.
The report, which explores in detail Moscow's role in the Ukraine crisis, was released May 12 in limited numbers by Nemtsov's allies.
The U.S.-based payment system "does not offer the option of using its system to receive donations for political parties or political causes in Russia," according to screenshot of a letter from Paypal posted online Thursday by a Russian activist involved in the fundraising, Vsevolod Chagayev.
He called the phrasing "delirious" in a Twitter message.
A payment system operated by Russia's search engine Yandex was still functioning for the project, Chagayev said.
The authors of the report, called "Putin.War," say it provides data and testimony that demonstrate Russia's support for pro-Moscow separatists battling Ukrainian government forces in the country's east.
Based on interviews with the families of Russian soldiers and their representatives, the report said that at least 220 Russian troops were killed in eastern Ukraine in two major episodes of fighting — one last year and one early in 2015.
Nemtsov began working on the report when relatives of dead servicemen approached him after failing to receive military death payments from the government, his allies said.
The dissident leader had wanted to distribute the report widely to combat the Kremlin's "propaganda" about the war, his allies quoted him as saying.
Only 2,000 copies of the report have been published so far, but activists have said they would use crowdfunding to release a bigger print run.