Hundreds of German politicians including Chancellor Angela Merkel have had personal details hacked and published online, reports say.
Contacts, private chats and credit card details were put out on Twitter which belong to figures from every political party except the far-right AfD.
Data from celebrities and journalists also appear to have been leaked.
It is unclear who was behind the hack, which emerged on Twitter last month in the style of an advent calendar.
How extensive was the attack?
The true extent of damage caused by the leak is not yet known although Justice Minister Katarina Barley said it was a “serious attack”.
“The people behind this want to damage confidence in our democracy and institutions,” she said.
Germany’s federal office for information security (BSI) said it was investigating the hack and said government networks were not affected, as far as it was aware.
Although no politically sensitive documents appear to have been published, the sheer extent of personal data leaked suggests the consequences could be considerable, says RBB reporter Michael Götschenberg, who researched the hack.
The Twitter account, followed by 17,000 people, appeared to be linked to an internet platform based in Hamburg, he said. Although documents had been posted on the account last month, it was not until Thursday evening that officials became aware of the hack.
Who was targeted?
National and local political figures have had their details hacked.
Even Chancellor Angela Merkel was caught up in the attack, reports say. Her email address and several letters to and from the chancellor appear to have been published.
The main parliamentary groups and their MPs were all affected, including the ruling centre-right and centre-left parties, as well as the Greens, left-wing Die Linke and FDP. Only the AfD appears to have escaped the hack.
Journalists from public broadcasters ARD and ZDF were targeted as well as TV satirist Jan Böhmermann, rapper Marteria and rap group K.I.Z, reports say.
German politicians have been targeted before.
Russia was accused of a series of cyber attacks that stole data from computers in the German parliament, the Bundestag, in 2015.
Last year the German government’s IT network came under a fresh attack amid reports that Russian hackers were also to blame.