Germany's foreign intelligence service BND long spied on journalists of the BBC, The New York Times, Reuters and other media, news weekly Der Spiegel reported Friday.

Media rights group Reporters Without Borders labelled the alleged surveillance 'a monstrous attack on press freedom', voiced fears the eavesdropping was ongoing and said it was planning legal action, according to Der Spiegel.

The magazine, which has extensively worked with US fugitive intelligence contractor Edward Snowden and reported on US and German espionage scandals, only cited documents it had seen.

While it is unknown exactly who the BND spied on, news of the surveillance is a culmination of the three year inquiry that resulted in German Chancellor Angela Merkel giving evidence last week.

Germany's foreign intelligence service BND listed at least 50 telephone and fax numbers and email addresses of journalists or newsrooms on its list of 'selector' keywords for surveillance since 1999. The list featured several BBC numbers

A number of The New York Times in Afghanistan was also on the list, as were mobile and satellite phone numbers of news agency Reuters in Afghanistan, Pakistan and Nigeria

Der Spiegel reported that the BND had listed at least 50 telephone and fax numbers and email addresses of journalists or newsrooms on its list of 'selector' keywords for surveillance since 1999.

These included several dozen numbers of the British Broadcasting Corporation at its London headquarters and in Afghanistan, as well as of the BBC World Service, it said.

A number of The New York Times in Afghanistan was also on the list, as were mobile and satellite phone numbers of news agency Reuters in Afghanistan, Pakistan and Nigeria.

The BND declined to comment, Der Spiegel said in an early excerpt of an article to be published in full in its weekly edition which hits news stands Saturday.

A BBC spokeswoman said: 'We are disappointed to hear these claims.

'The BBC's mission is to bring accurate news and information to people around the world and our journalists should be able to operate freely and safely, with full protection for their sources.

'We call upon all governments to respect the operation of a free press.'

While it is unknown exactly who the BND spied on, news of the surveillance is a culmination of the three year inquiry that resulted in German Chancellor Angela Merkel giving evidence last week

Meanwhile, Merkel admitted on earlier this month that she did not know how closely Germany's spies cooperated with their US counterparts until 2015, well after an uproar over reports of United States bugging of her cellphone.

Merkel, who is running for a fourth term in September, told a parliamentary committee that she assumed Germany's BND foreign intelligence agency would not help the US National Security Agency (NSA) to spy on European politicians and companies.

German media revealed in 2013 that the NSA had bugged Merkel's cellphone, which strained relations with Washington.

Opposition lawmakers wanted to know if Merkel knew that the BND was helping the NSA spy on European allies when she uttered those words. She told the committee that she had assumed at the time that 'the BND would not do such thing'.

The German parliament set up the investigation in 2014.

Surveillance is a sensitive issue in Germany where East Germany's Stasi secret police and the Nazi era Gestapo kept a close watch on the population.

Germany's highest court last year rejected a bid by opposition politicians to make the government disclose to the investigating committee the surveillance targets it worked on with the NSA.

German lawmakers in October approved a law to tighten oversight of the BND, but critics said the new rules do exactly the opposite.