The Russian Central Electoral Commission found there 736,000 fewer registered voters in the country than there were for the March 4 presidential election.
CEC head Vladimir Churov said the difference was negligible, however.
"It's a seasonal fluctuation," he was quoted by state-run news agency RIA Novosti as saying. "This (figure) is less than 1 percent (of the total voter population)."
Criticism of the Russian government erupted following State Duma elections in December. Mass protests erupted when Vladimir Putin won a third non-consecutive term as president early this year. Duma elections, which saw the ruling United Russia party secure its dominance, and presidential elections were viewed as slanted in Putin's favor.
U.N. High Commissioner for Human Rights Navi Pillay last month reminded the Kremlin that government criticism was sometimes "uncomfortable" but peaceful opposition was a "crucial" element of a developed society.