WASHINGTON — The Obama administration on Friday officially accused Russia of attempting to interfere in the 2016 elections, including by hacking the computers of the Democratic National Committee and other political organizations.
The denunciation, made by the director of national intelligence and the Homeland Security Department, came as pressure was growing from within the administration and some lawmakers to hold Moscow accountable for a set of actions apparently aimed at sowing discord around the election.
‘‘The US intelligence community is confident that the Russian government directed the recent compromises of e-mails from US persons and institutions, including from US political organizations,’’ said a joint statement from the two agencies. ‘‘These thefts and disclosures are intended to interfere with the US election process.’’
The statement came on the same day that the United States directly accused Russia of war crimes in Syria because of what it says is deliberate targeting of civilians. In other signs of the tensions between the Washington and Moscow, Russia‘s State Duma on Friday approved a treaty allowing Russian troops to stay in Syria indefinitely, while Russia’s military said it is considering reopening bases in Cuba and Vietnam.
The Democratic National Committee publicly disclosed the hacking of its system in June, saying its investigation determined that Russian government hackers were behind the breach.
That was followed shortly after by a major leak of DNC e-mails, some so embarrassing that they forced the resignation of the DNC chairwoman, Representative Debbie Wasserman Schultz of Florida, on the eve of the Democratic National Convention.
The administration also blamed Moscow for the hack of the Democratic Congressional Campaign Committee and the subsequent leak of private e-mail addresses and cellphone numbers of Democratic lawmakers.
A series of other leaks of hacked material followed.
The digitally purloined material has appeared on websites such as DCLeaks.com and WikiLeaks. It has included the private e-mails of former secretary of state Colin Powell and aides to former secretary of state and Democratic presidential candidate Hillary Clinton.
An online persona calling himself Guccifer 2.0 has claimed responsibility for posting the material.
Those sites and that persona are ‘‘consistent with the methods and motivations of Russian-directed efforts,’’ the joint statement said. ‘‘We believe, based on the scope and sensitivity of these efforts, that only Russia’s senior-most officials could have authorized these activities.’’
President Vladimir Putin of Russia has denied any connection to the hacks. ‘‘I know absolutely nothing about it,’’ he said in an interview last month with Bloomberg News. ‘‘Russia has never done anything like this at the state level.’’
Moreover, Putin said, ‘‘I could never even imagine that such information would be of interest to the American public.’’
Russia again dismissed the US claims on Friday. ‘‘This is again some kind of nonsense,’’ Kremlin spokesman Dmitry Peskov told the Interfax news agency.
‘‘Every day there are tens of thousands of attacks on Putin’s website. Many of the attacks can be traced to the US. We’re not blaming the White House or Langley every time.’’
“Langley’’ is a reference to the CIA’s headquarters in Virginia.
The Obama administration noted that attempts to interfere in other countries’ political processes are not new to Moscow. Russian hackers have used hacking and other techniques to influence public opinion in Europe and Eurasia, it noted.
On the eve of a critical postrevolution presidential vote in Ukraine in 2014, for instance, a digital assault nearly crippled the country’s central election commission website.
The White House declined to say Friday whether the formal attribution of the political hacking would trigger sanctions against Russia, the Associated Press reported.
A senior Obama administration official said the United States would respond ‘‘at a time and place of our choosing,’’ but any retaliation may not take place in the open.