BERLIN

German official websites suffered major hacking attacks disrupting essential services, authorities said on Thursday.

In the capital Berlin, citizen services portal and websites of police were severely impacted by DDoS attacks.

Ralf Kleindiek, the chief digital officer of Berlin, told public broadcaster RBB that they experienced “the biggest attack” targeting the websites of the state administration on Wednesday.

According to initial investigation, no data was leaked or stolen, but many official websites were temporarily unavailable. Services started to resume on Thursday.

Police spokeswoman Beate Kardels said authorities opened investigation into the cyberattacks.

“We know that there are letters of confession, allegedly from a Russian cyber group, but we have to wait for the outcome of the investigation, she said.

Websites of police and local authorities in federal states of Brandenburg, Schleswig-Holstein, Lower Saxony, Saxony-Anhalt, Thuringia, Mecklenburg-Western Pomerania, and Saarland were also targeted by hackers on Tuesday and Wednesday, according to authorities.