The incident occurred on Saturday. Mr Iliescu, leaving the Black Sea port of Constanta after Navy Day ceremonies, reportedly jumped out of his limousine and confronted about 100 demonstrators.
Among them was Paul Pirvu, a reporter for the local newspaper, Telegraful. He said the President 'came straight at me and grabbed . . . my collar and part of my neck'. Mr Pirvu said the President's grip left some bruises.
Alexandru Mihalcea, a reporter for the leading opposition daily, Romania Libera, who was also present, confirmed the story. He said Mr Iliescu's bodyguards beat up journalists and tried to confiscate film.
Mr Iliescu's spokesman, Alexandru Mironov, said Mr Iliescu approached the crowd and 'conducted a dialogue' with Mr Pirvu but denied any physical assault. He said the President's office would try to strip Mr Pirvu, whom he termed 'a hood', of his journalist's accreditation.
The Association of Romanian Journalists, the country's main press union, backed Mr Pirvu's version and offered to fund any legal action against Mr Iliescu.
Iliescu, a former Communist minister, came to power in the 1989 revolution that overthrew dictator Nicolae Ceausescu. Despite persistent charges that he has blocked reforms, he is expected to win re-election.