Democrats in Congress, including the party's Senate leader, Harry Reid, have asked the FBI to investigate concerns that the Russian government may be attempting to undermine the U.S. presidential election through cyberattacks that could include tampering with voting results.
"The prospect of a hostile government actively seeking to undermine our free and fair elections represents one of the gravest threats to our democracy since the Cold War," Reid said in a letter to FBI Director James Comey.
Reid's letter, dated Saturday, was obtained by The New York Times and shared on its website Monday.
It was followed Tuesday by a letter from four Democrats asking Comey to assess whether campaign officials working for Republican presidential candidate Donald Trump may be colluding with Russian interests to carry out recent hacks against the Democratic National Committee and Democratic Congressional Campaign Committee in order to "interfere with the U.S. presidential election."
That letter was signed by Representatives Elijah Cummings, John Conyers, Elliot Engel and Bennie Thompson, each of whom serves as the top Democrat on a different congressional committee. Republicans control both the House of Representatives and the Senate.
Comey, speaking at a cybersecurity conference Tuesday, declined to give details about what the FBI was probing in connection with the political hacking but indicated the agency was closely watching what foreign countries are doing.
"We take very seriously any effort by any actor, ... especially nation states, that moves beyond the collection of information ... and offers the prospect of an effort to influence the conduct of affairs in our country, whether that is an election or something else," he said.
The two letters followed a spate of hacking attacks targeting U.S. political databases, including some that officials and cybersecurity experts have blamed on hackers working for the Russian government. Kremlin officials have denied that.
The FBI examined breaches in voter registration databases in Illinois and Arizona but did not specify who might have been behind them.
Reid said that the threat of Russian government tampering in the election was "more extensive than widely known and may include the intent to falsify official election results."
He also voiced concerns about possible Russian government efforts to manipulate Trump's campaign ahead of the November 8 election, and to use it as a vehicle to advance the interests of Russian President Vladimir Putin.