Politicians at the federal, state and European level had been affected, government spokeswoman Martina Fietz said on Friday, as state prosecutors announced they were looking into the leak.

Much of the data published online concerns mobile phone numbers and addresses, but in some cases also highly personal information such as identity cards, chats, letters, invoices or credit card information.

Fietz warned that false information could also be included among the authentic data.

Chancellor Angela Merkel is among those caught up in the leak, but no sensitive information from her or her office had been published online, Fietz said.

Her fax number, email address and several letters both to and from Merkel were among the leaked data.

Describing it as a "severe attack," Justice Minister Katarina Barley said: "The author of the attack wants to damage trust in our democracy and in our institutions."

The perpetrator should be found immediately and their motives clarified, she said, suggesting a political motive.

"Criminals and those who back them should not be allowed to dictate any debate in our country," she added.

Her comments were echoed by the head of the far-left Die Linke faction in parliament, Dietmar Batsch, who said he was "badly shocked" and called it "an attack on democracy."

The owner of the Twitter account that released the data - which is now blocked online - used terms such as security research, artist, satire and irony to describe what he or she was doing.

Links to the data appeared daily on the Twitter feed in December in an advent-calender style, but it was only noticed more recently.

A politician from the Social Democratic Party, Helge Lindh, told DPA that he learned of the leaks on Thursday evening.

All parties represented in the Bundestag with the exception of the far-right Alternative for Germany have apparently been affected.

It has also hit celebrities outside the political sphere, as well as journalists and musicians.

The government was checking whether the leak was indeed the result of an attack from outside hackers or whether it could have been carried out by someone who already had access to the data.

The government's internal network was not compromised, the Federal Office for Information Security said on Twitter.

State prosecutors had started to examine the leak as part of a so-called "observation" procedure, a Justice Ministry spokeswoman said.

The aim is to evaluate the significance of the leak and any possible criminal aspect that requires further investigation.

The liberal FDP party has launched separate legal proceedings after 28 of its members were affected by the leak, the party said on Friday.

Australian Associated Press