Russia has accused the United States of interfering in its parliamentary election, which is taking place in just over a week.
The app 'Smart Vote' of imprisoned Kremlin critic Alexei Navalny was "connected in one way or another with the Pentagon," a spokesperson for the Russian Foreign Ministry, Maria Sakharova, told state broadcaster Radio Rossii.
Navalny's supporters are using the app to call on Russians to vote against the Kremlin United Russia party in the elections, which are taking place from September 17 to 19.
The associated homepage has been blocked in Russia for several days. The authorities have also prohibited internet search engines Google and Yandex from displaying the term 'Smart Vote' in search results.
Sakharova also referred to a conversation between Russia's Deputy Foreign Minister Sergei Ryabkov and the US Ambassador in Moscow, John Sullivan, on Friday.
Sullivan had been told that the Russian side had "irrefutable evidence" of violations of the law by US internet giants in connection with the upcoming Duma election, it said in a statement.
A security issue
From the US side there was initially no reaction to the allegations.
Tatyana Stanovaya, a political scientist, said Zakharova's statements were an attempt to turn the 'smart vote' into a national security issue.
She said this would enable the Russian authorities to take further action in the longer term in order to contain attempts by Navalny's team to call a protest vote, in comments she posted on Telegram.
