Technical trade secrets were stolen from the steel production and manufacturing plant design divisions of Thyssenkrupp in cyber attacks earlier this year, the company announced Thursday.

In breaches discovered by the firm's internal security team in April and traced back to February, hackers stole project data from a variety of divisions, Thyssenkrupp said while declining to explain why the company had not previously disclosed the attacks.

The steelmaker attributed the breaches to unnamed attackers in southeast Asia in what it said were "organized, highly professional hacker activities."

More to come?

Cyber attacks on banks or retailers have become a frequent phenomenon globally, causing widespread consumer data breaches and mounting financial losses, but revelations of industrial espionage are still rare.

Thyssenkrupp's belated disclosure came just one week after an attack on nearly 1 million routers caused outages for Deutsche Telekom customers in Germany.

German business magazine "Wirtschaftswoche" reported the attacks on Thyssenkrupp hit sites in Europe, India, Argentina and the US.

A criminal complaint was filed with police in the state of North Rhine-Westphalia, and an investigation is ongoing.

Thyssenkrupp noted the infected computer systems had been cleansed and were now subject to constant monitoring against potential intruders.

hg/jd (Reuters, dpa)