Outraged politicians and other prominent public figures are pressuring German authorities to get to the bottom of a massive data breach, in which stolen personal data was published by an anonymous Twitter account, German news agency DPA reported on Sunday.

Around 50 of the nearly 1,000 cases of leaked data are considered severe, meaning that personal data, photos and correspondence were made public, security sources told DPA on Sunday.

Former and current elected officials are among the 994 people affected by the data breach, with the vast majority of them hit solely with the publication of their contact data, the sources said.

German Chancellor Angela Merkel and President Frank-Walter Steinmeier were targeted, while celebrities and journalists were also among the victims, DPA said.

The 50 more serious cases are currently the focus of ongoing investigations, according to the sources.

The data was released in daily tweets throughout December in the style of a Christmas advent calendar but only attracted national attention on Friday. The Twitter account, named "G0d" (@_0rbit), has since been suspended. It is unclear who was behind the attack.

German authorities charged with data security have come under fire. The Federal Office for Information Security (BSI) first became aware of the scale of the data leak in January, according to DPA.