BERLIN — A 27-year-old informatics student in southern Germany was identified in news reports on Thursday as the first German citizen known to be under surveillance by the National Security Agency since it was revealed last year that the agency had once tapped the cellphone of Chancellor Angela Merkel.

The news came on the same day that two former American security officials testified to a parliamentary inquiry about reports of sweeping digital surveillance and monitoring in Germany by American intelligence, which touched off a major controversy and put strains on German-American relations.

The student, Sebastian Hahn of Erlangen in Bavaria, said he had been active for six years in the Tor network, a group that works to encrypt digital communications, and that he had rented space on a computer in Nuremburg that he said was one of several around the world that direct other computers involved in Tor. Two German state broadcasting channels reported that there was evidence that the N.S.A. was tracking the Nuremberg computer as part of an operation called “XKeyscore.” A server at the Massachusetts Institute of Technology that is used by Roger Dingledine, a well-known web activist, was also tracked in the operation, the German broadcasters reported.

After classified materials leaked by the former security contractor Edward J. Snowden indicated in June 2013 that the N.S.A. had swept up the electronic communications of millions of Germans, the government sought reassurances from Washington that no German laws had been broken. It appeared to receive such assurances and said the affair was settled, only to have it flare up anew when word of the eavesdropping on Ms. Merkel emerged in October. That news prompted lawmakers here to begin a formal inquiry, which is expected to last at least two years.