Peruvian President Alan Garcia has denied slapping a young man who insulted him when he visited a hospital last weekend.
The alleged victim says he was struck by the president and then beaten up by his bodyguards after he called Mr Garcia corrupt.
Mr Garcia initially denied the incident had taken place.
He then said he had responded indignantly when insulted, but had not hit the man.
The incident has caused considerable controversy in Peru, where insulting the head of state is an offence.
President Garcia was visiting Edgardo Rebagliati hospital in Lima with his daughter last Saturday when the confrontation took place.
Richard Galvez, 27, a volunteer worker at the hospital, says he shouted "corrupt" at Mr Garcia when he saw him pass by.
Mr Galvez alleges the president turned on him and struck him in the face.
He further alleges he was then beaten by some of Mr Garcia's security guards, while other hospital workers and patients shouted in protest.
The incident was widely reported in Peruvian newspapers, quoting witnesses.
President Garcia initially denied there had been a confrontation.
He later said he had responded with a gesture and told Mr Galvez to "Go to hell" after he was insulted, but had not hit the man.
And he said he was right to be indignant.
"Nobody shows me disrespect, much less to the president, and much less in front of my daughter or mother", he said.
"It is impossible that someone calls you 'corrupt' to your face and you stay silent in front of your daughter".
Another man later came forward and said it was he, and not the president, who struck the volunteer, saying he was enraged at hearing insults directed at the president's mother.
It is not the first time Mr Garcia has been accused of lashing out in public, says the BBC's Dan Collyns in Lima.
In 2004 he is alleged to have kicked a man with mental health problems who passed in front of him as he took part in a protest march.