The Central Intelligence Agency (CIA) has concluded that Russia tried to help elect Donald Trump president of the United States, Washington Post reports.
US officials told leading newspapers that US intelligence agencies believe Russia acted covertly to boost Trump in the election race.
A report in the New York Times says the agencies had “high confidence” about Russian involvement in hacking.
Russian officials have repeatedly denied the hacking accusations, and Trump’s team dismissed the CIA line, saying: “These are the same people that said Saddam Hussein had weapons of mass destruction.”
On Friday, US President Barack Obama ordered an investigation into a series of cyber-attacks, blamed on Russia, during the US election season.
The hacks targeted emails at the Democratic Party and a key aide to presidential nominee Hillary Clinton.
In October, US government officials pointed the finger at Russia, with accusations of meddling with the campaign.
According to the New York Times, senior administration officials say they are confident that Russian hackers also infiltrated the Republican National Committee’s computer systems as well as those of the Democratic Party, but did not release information obtained from the Republican networks.
Intelligence agencies say the Russians passed on the Democrats’ documents to WikiLeaks, the Times also reported.
Democrats reacted furiously when email accounts of the Democratic National Committee and Mrs Clinton’s campaign chairman, John Podesta, were hacked. The emails were revealed by WikiLeaks and posted online.
Quoting an unnamed “senior US official”, the Washington Post said “intelligence agencies” had “identified individuals with connections to the Russian government who provided WikiLeaks with thousands of hacked emails from the Democratic National Committee and others, including Hillary Clinton’s campaign chairman”.
At one point in the campaign, Mr Trump publicly encouraged Russia to “find” Mrs Clinton’s emails, although he later said he was being sarcastic.