SEOUL (Reuters) - A South Korean intelligence agent found dead in an apparent suicide left a note denying his team had used spyware to tap the mobile phones and computers of private citizens in the latest scandal involving the spy agency.

Police in the suburban district of Yongin south of Seoul said on Sunday that a 46-year-old man found dead in his car of an apparent carbon monoxide poisoning was an employee of the National Intelligence Service (NIS).

The note released by police, who confirmed the writing to be the agent's, said there was no spying whatsoever against domestic citizens or related to elections.

"I believe excessive zeal for work has created this situation," the agent, whose identity or rank in the intelligence service was not disclosed, said in the note.

The case comes after a rare public admission last week by the agency that it had purchased a spyware from an Italian firm used to eavesdrop mobile phone and computer communication but it was intended for research or for use against foreign targets.

The revelation marks the latest in a series of scandals centered on the intelligence service that has struggled to shed the image of a political tool of sitting presidents and to reform to focus more on counter espionage against North Korea.

A former spy chief under President Park Geun-hye's predecessor is fighting a guilty conviction for trying to influence the 2012 election that brought the conservative leader to power.

Park denied benefiting from attempts by NIS agents to sway voters but said after another scandal at the intelligence agency last year that more could be done to reform it.

Park's father, Park Chung-hee, was assassinated in 1979 by the disgruntled head of the agency's precursor at the peak of a power struggle that involved the late president's close aides.

(Reporting by Jack Kim; Editing by Michael Perry)