Germany's "Frankfurter Allgemeine Sonntagszeitung" (FAS) quoted a high-ranking security official who said it was "highly plausible" that a cybertheft of files from a German parliamentary inquiry in 2015 was conducted by Russian hackers.
Russia has repeatedly denied such spying, with Foreign Minister Sergei Lavrov saying in October that such claims were unproven.
In early 2015, a cyberattack took place on the database of the Bundestag parliament's administration, prompting widespread alarm in Berlin followed by calls to improve Germany's cybersecurity.
FAS reported Sunday that 2,420 secret files published two weeks ago by WikiLeaks were documents that had been stored electronically at parliament in late 2014 and early 2015 for the Bundestag's own inquiry into the NSA.
The inquiry panel was examining the extent of US National Security Agency (NSA) interactions with Germany's BND foreign intelligence service triggered by Edward Snowden's disclosures of rampant surveillance conducted by the NSA, BND and other intelligence agencies around the world.
No other Bundestag files, and none from the period beyond January 2015, had been disclosed by WikiLeaks, FAS reported.
The paper quoted a high-ranking security official as saying: "There is a high plausibility that the files originated from Russia's cyberattack on the Bundestag in early 2015."
Parallels with hacking of US Democrats?
FAS said security sources saw parallels between the German attack and the theft of messages from the server of the US Democratic Party - also published by WikiLeaks - that last July forced the resignation of party chairwoman Debbie Wasserman Schulz for allegedly favoring candidate Hilary Clinton over Bernie Sanders.
US President-elect Trump on Saturday rejected reported US intelligence findings carried by US newspapers that Russia had interfered in November's US presidential election.
In an interview for Fox News Sunday he described such claims as "ridiculous." In July, Trump said he hoped Russian hackers would reveal messages that had been deleted from Hillary Clinton's email server. The FBI twice said Clinton's behavior was careless but not criminal.
US media reported being told by senior US intelligence officials that probes had established with "high confidence" that not only did Russian counterparts direct the hacking of the Democratic Party but did so to undermine Clinton.
Two leading Republican senators, John McCain and Lindsey Graham, joined two other senators, Democrats Chuck Schumer and Jack Reed, on Sunday, saying: "Recent reports of Russian interference in our election should alarm every American."
"This cannot become a partisan issue. The stakes are too high for our country, said the senators.
Impact denied at the time
In Berlin, a senior opposition Greens member in the NSA panel, Konstantin von Notz, expressed skepticism, telling the "Tagesspiegel" newspaper that the NSA "inquiry committee was not affected" by the 2015 cyberattack.
The panel had been set up in 2014 to look into suggestions by former NSA contractor Edward Snowden that the NSA had eavesdropped on German citizens and politicians.
Fears for Germany's 2017 election year
Fears were expressed Sunday that Germany's 2017 federal election and three regional elections could be subjected to manipulative attempts by cyberoperators.
Wolfgang Bosbach, a conservative ally of Chancellor Angela Merkel, told the "Kölner Stadt-Anzeiger" (KStA) newspaper: "The risk of exertion of influence through deliberate infiltration from outside with the aim of manipulating facts or opinion exists generally."
Rolf Mützenich, the Social Democrat parliamentary group's foreign policy spokesman told the KStA: "During campaigning we will have to prepare ourselves for distortion and false stories."
Christian Lindner, the chairman of the liberal pro-business Free Democrats (FDP) claimed that the populist, anti-immigrant Alternative for Germany (AfD) party would try to profit from "Russian-controlled online media."
ipj/sms (AFD, dpa, Reuters)