Berlin (AFP) - Germany's chief prosecutor on Friday suspended a treason probe against Internet security bloggers that had sparked a storm of protest from journalist and politicians.

Harald Range said "in view of the great good of freedom of the press and expression" he would let the investigation rest, the daily Frankfurter Allgemeine Zeitung reported online.

News of the probe against the blog Netzpolitik.org -- Germany's first treason case against media since the 1960s -- had sparked a wave of indignation and expressions of solidarity.

The blog had published documents on plans to step up Internet surveillance by Germany's domestic security agency, whose chief Hans-Georg Maassen then filed a criminal complaint.

Range -- whose office was not immediately available for comment to AFP -- said the case was suspended while experts determine whether the documents indeed constitute "state secrets".

Writers of Netzpolitik (Net politics), which focuses on "digital civil rights" and was in 2014 awarded Germany's Grimme Online Award, had reacted defiantly to the probe, stating that "we will not be intimidated".

The German Journalists Association condemned the investigation for treason, which carries between one year and life in jail, as an "impermissible attempt to silence two critical colleagues".

On Twitter #Landesverrat (#treason) became a top trending topic, and news website Spiegel Online said the accusation was widely seen as a "knighting" of the journalists.

The German Association of Lawyers demanded the abolition of the charge of treason for journalists.

Another website republished the contentious articles and challenged the state to investigate it too, while a Green Party lawmaker said he had donated money to Netzpolitik and tweeted an image of its bank details so others could follow suit.

The controversy flared amid continued debate over sweeping online surveillance by the US National Security Agency (NSA) revealed by fugitive intelligence contractor Edward Snowden and the degree of German cooperation.

Netzpolitik founder Markus Beckedahl, one of the two writers named in the probe, charged it was increasingly clear that the German government is "knee-deep in the swamp of NSA and Co".

"We see this as clear attempt of intimidation by the federal government -- or our security agencies, backed by the federal government -- against investigative journalists and their sources," he told national news agency DPA.

The chair of the parliamentary judicial committee, Renate Kuenast of the Greens party, said the case "infuriates me and is a constitutional disgrace", adding that "if there were no investigative journalism, we would know nothing."

Many commentators drew parallels to a treason case against news weekly Der Spiegel after it published a report in 1962 that pointed to shortcomings in the German armed forces.

The Hamburg-based weekly was raided by police and its editors arrested, sparking street protests in support of Der Spiegel.

A court later ruled in its favour and the defence minister stepped down, in what was seen as a victory for democracy and cemented its reputation for investigative journalism.