In an interview with German weekly "Bild am Sonntag," domestic intelligence chief Hans-Georg Maassen defended criminal charges against Netzpolitik reporters Andre Meister, Markus Beckedahl and an "unknown source" for publishing state secrets online.

Maassen, president of Germany's Federal Office for the Protection of the Constitution (BfV), said that "to continue the fight against extremism and terrorism…it was necessary to guard against the publication of documents classified as confidential or secret."

However, an investigation into German news site Netzpolitik's reporters was frozen by Federal Prosecutor Harald Range on Friday.

"Everything else is now in the hands of the justice ministry," Maassen told the German periodical.

Criticism of 'treason' charge

Meister and Beckedahl were informed on July 24 that they were suspects in an investigation of two articles published on the news site that included "classified" and "confidential" documents.

However, the initial charges for "treason" were widely criticized, with German journalist union DJV calling it an attack on press freedom.

"From the very beginning, the charges against our alleged source(s) were politically motivated and targeted to crush the necessary public debate about Internet surveillance post-Snowden," wrote Netzpolitik's Anna Biselli in a statement on the site.

"Whistleblowers in the public interest need protection, not prosecution for 'treason,'" Biselli added.

On Saturday, demonstrators gathered in the German capital Berlin to protest the charges levied against the reporters with the popular German website.

ls/gsw (AFP, Reuters, dpa)