Witnesses told the celebrity gossip website a fan approached Kutcher while he was in a VIP area watching Nick 13 and Dwight Yoakam performances. When he went to shake the fan's hand, a security guard allegedly pushed the two apart.
The guard demanded Kutcher be ejected after violent shoving between the two, but the actor left on his own, witnesses said.
Meanwhile, the music festival -- in its sixth year -- is earning a reputation as being more rowdy than its rock counterpart, the Coachella Valley Music and Arts Festival, held earlier this month in the same desert area of California, the Los Angeles Times reported Saturday.
At the halfway mark of the Stagecoach festival, police had arrested 53 people for various drug- and alcohol-related offenses, said Benjamin Guitron of the Indio Police Department.
A total of 80 people were arrested during the entire Coachella festival this year, the Times said. At last year's Stagecoach festival, 171 people were arrested.
Police ramped up security this year, banning camping in tents and sleeping in cars at the Empire Polo Club grounds where the festival is held.
Florida bear attack: Black bear mauls woman's face
Texas principal bans speaking Spanish, stirs controversy