Germany's Interior Ministry said on Saturday that there had been a "serious cyber attack on the network of the CDU," referring to the country's largest opposition party also known as the Christian Democrats. 

The ministry said that the BSI, Germany's federal IT security agency, and the domestic intelligence agency, the BfV, were "intensively working on repelling and investigating the attack, and on preventing any further damages."

A spokesperson for the CDU told the Reuters news agency that the party was "cooperating closely" both with security services and with external security experts. 

The party said in a separate statement that they had taken down and isolated part of their IT infrastructure.

Investigations launched, indications of 'very professional actor'

In its first public comments, the ministry did not divulge what kind of attack had targeted the party nor the extent of the attack.

"However, the nature of the attack points to a very professional actor," German news agency DPA quoted an unnamed Interior Ministry spokesman as saying. It cited sources close to the government as saying the case was being taken very seriously. 

Interior Minister Nancy Faeser (from the rival Social Democrats) had been in contact with CDU leader Friedrich Merz to discuss the case.

The incident comes almost exactly one week ahead of the European Parliament elections, with polling day in Germany on June 9 as it is in the majority of EU member states. 

"The BfV will issue a warning to all [political] parties in the German Bundestag [parliament] regarding the current attack," the Interior Ministry said. "Our security agencies have intensified all protective measures against digital and hybrid threats and are informing people about the dangers." 

Russia accused of being behind similar attack on SPD

The CDU's center-left rival the SPD (or Social Democrats) was also the victim of a cyberattack last year, with email accounts being hacked.

In that case, the government blamed a Russian military intelligence unit for orchestrating the hack and summoned a high-ranking Russian diplomat to the Foreign Ministry in Berlin. 

That hack also targeted German companies in areas like logistics, defense, aerospace and IT services sectors. The SPD later said that a security vulnerability, not identified at the time, in Microsoft software had enabled the hack.

msh/ab (AFP, dpa, Reuters)