Leading Democrats on the congressional intelligence committees have accused Russia of trying to influence the November 8 U.S. election via computer hacking and called on Russian President Vladimir Putin to "order a halt to this activity."
U.S. Senator Dianne Feinstein (Democrat-California) and Representative Adam Schiff (Democrat-California) said in a strongly worded statement that "based on briefings we have received, we have concluded that the Russian intelligence agencies are making a serious and concerted effort to influence the U.S. election."
"At the least, this effort is intended to sow doubt about the security of our election and may well be intended to influence the outcomes of the election -- we can see no other rationale for the behavior of the Russians," they said.
The lawmakers added that they "believe that orders for the Russian intelligence agencies to conduct such actions could come only from very senior levels of the Russian government."
Officials in President Barack Obama's administration have said that Russia or its proxies are responsible for hacking political party organizations, but have stopped short of directly blaming Russia in public.
The White House said on September 16 it was trying to build a legal case against Russian hackers it believes are behind recent leaks aimed at disrupting the U.S. presidential election.
At the same time, Congress said it was looking at perhaps using sanctions against Russia for the hacks, media reports said.
Reuters said the administration believes that two Russian intelligence agencies -- the military's GRU and the civilian intelligence agency -- are behind recent cyberattacks against the Democratic National Committee (DNC) and former top Republican diplomats.
Meanwhile, an image purported to be a scanned copy of first lady Michelle Obama's passport was leaked online on September 22 along with personal e-mails belonging to a former staffer for Democratic presidential candidate Hillary Clinton.
Feinstein and Schiff said in their statement that they call on Putin "to immediately order a halt to this activity."
"Americans will not stand for any foreign government trying to influence our election," they said. "We hope all Americans will stand together and reject the Russian effort."
There was no immediate public response to the lawmakers' statement from Russian officials.
DNC officials and the Clinton campaign have suggested that Russia is attempting to boost the electoral chances of Clinton's Republican rival, businessman and former reality TV star Donald Trump, who has said he would seek to improve battered bilateral ties with Russia if he is elected to the White House.
Both Trump and the Kremlin have dismissed these suggestions as baseless.
Trump has spoken positively about Putin, saying earlier this month that the Russian president has been more of a leader for his country that Obama has been for the United States.