German federal prosecutors said Thursday they are probing an alleged hacking attack against lawmakers ahead of this month's German election that Berlin has blamed on Russia.

"I can confirm that we have opened an investigation on suspicion of espionage," a spokesman for the prosecutor's office told AFP when asked about accusations made this week by the German government about "phishing" attacks against MPs by Russian intelligence.

Berlin on Monday strongly criticised what it called Russian attempts to influence the September 26 election of a new parliament and Angela Merkel's successor as chancellor.

It pointed the finger at hackers from Russia's "Ghostwriter" group which reportedly specialises in spreading disinformation. German intelligence believes they have been trying to gain access to the private email accounts of federal and regional MPs.

German authorities say Russia's military intelligence service GRU is behind the attacks and has targeted in particular politicians from Germany's ruling Christian Democrats and Social Democrats.

The head of German's domestic intelligence service, Thomas Haldenwang, warned in July that such hackers had successfully made off with personal information that could be exploited in the weeks before the general election.

The case comes at a time of particularly fraught ties between Berlin and Moscow over a series of espionage cases, the poisoning and jailing of Kremlin critic Alexei Navalny as well as repeated cyberattacks against the West.