The head of Germany’s domestic intelligence agency has accused Russian rivals of gathering large amounts of political data in cyberattacks and said it was up to the Kremlin to decide whether it wanted to put it to use ahead of Germany’s September elections.

Moscow denies it has in any way been involved in cyberattacks on the German political establishment.

Hans-Georg Maassen, president of the BfV agency, said in Potsdam that “large amounts of data” were seized during a May 2015 cyberattack on the Bundestag, or Lower House of Parliament, which has previously been blamed on APT28, a Russian hacking group. Mr. Maassen repeated his warning from last December in which he said Russia was increasing cyberattacks, propaganda and other efforts to destabilise German society.

Links to Russian state

Some cyber experts have drawn clear links between APT28 and the GRU Russian military intelligence organisation.

Mr. Maassen said there had been subsequent attacks after the 2015 Bundestag hack that were directed at lawmakers, the Christian Democratic Union of Chancellor Angela Merkel, and other party-affiliated institutions.

Germany’s top cyber official last week confirmed attacks on two foundations affiliated with Germany's ruling coalition parties.