BERLIN - The US National Security Agency (NSA) tried to spy on industrial group Siemens with the help of German intelligence, Bild am Sonntag reported, in another potentially embarrassing development for Chancellor Angela Merkel.
Allegations that the domestic BND intelligence agency helped the NSA spy on European officials and firms have strained Germany's ruling coalition, which comprises Merkel's conservatives and the centre-left Social Democrats.
The scandal has also dented the personal popularity of Merkel, whose office is in charge of the intelligence service.
Snooping and eavesdropping by state agencies is a sensitive issue in Germany due to past abuses of privacy rights by the Nazis and by the East German Stasi secret police.
In its report on Sunday, Bild am Sonntag said the NSA had asked BND officials to spy on the European defence company Airbus and on Siemens.
The NSA justified its request by saying that Siemens had a contracted partnership with a Russian intelligence agency and that the Munich-based company had supplied communication technology within that context, the newspaper said.
In a statement sent to Reuters a Siemens spokesman rejected the NSA allegation about such a Russian connection.
Bild am Sonntag added it remained unclear whether the BND had accepted the NSA request. The German agency was not immediately available on Sunday to comment on the matter.
German Economy Minister Sigmar Gabriel and his Social Democrats (SPD) have said the list of "selectors" - including IP addresses, search terms and names which the BND had been tracking for the NSA - should be made public.
These are widely seen as being crucial to establishing whether the BND was at fault in helping the NSA, something that opposition parties say would amount to treason.
So far Merkel has ruled that out, saying it must be agreed with the United States. She has defended cooperating with US agencies to fight international terrorism and has said she would answer questions before a German parliamentary committee.
A close Merkel ally, Interior Minister Thomas de Maiziere, has faced calls to resign over the affair but denies he lied to parliament over the BND's co-operation with the NSA.