BERLIN — The U.S. National Security Agency has stepped up its surveillance of senior German government officials since being ordered by Barack Obama to halt its spying on Chancellor Angela Merkel, Bild am Sonntag paper reported on Sunday.

Revelations last year about mass U.S. surveillance in Germany, in particular of Merkel's mobile phone, shocked Germans and sparked the most serious dispute between the transatlantic allies in a decade.

Bild am Sonntag said its information stemmed from a high-ranking NSA employee in Germany and that those being spied on included Interior Minister Thomas de Maiziere, a close confidant of Merkel.

"We have had the order not to miss out on any information now that we are no longer able to monitor the chancellor's communication directly," it quoted the NSA employee as saying.

A spokesman for the German Interior Ministry said it would not comment on the "allegations of unnamed individuals."

To calm the uproar over U.S. surveillance abroad, President Obama in January banned U.S. eavesdropping on the leaders of close friends and allies of Washington.

Germans are especially sensitive about snooping due to their experiences in the Nazi era and in Communist East Germany, when the Stasi secret police built up a massive surveillance network.

Berlin has been pushing, so far in vain, for a "no-spy" deal with Washington. German Foreign Minister Frank-Walter Steinmeier is due to visit the United States on Thursday but he has said he doubts such a deal would have much effect.

Bild am Sonntag quoted a security adviser to Obama, Caitlin Hayden, as saying: "The United States has made clear it gathers intelligence in exactly the same way as any other states."

The mass-circulation paper said the NSA was monitoring 320 people in Germany - mostly politicians but also business leaders. Hayden said Washington did not spy on corporations in order to help U.S. firms gain competitive advantage.