"It may be something to look at, if this trend continues," McNamara said. "If you feel in fear, quietly and slowly walk away or cross the street to avoid them."

Skinheads are a periodic problem in the Square, police agencies report. The area commonly known as the Pit, near the subway kiosk, is patrolled by transit police, CPD and HUPD in an effort to avoid confrontations.

But police say violent episodes are rare.

"The problem is almost universal, but our worst problems come at night and when school lets out," said transit police spokesperson Brian A. Pedro.

The Anti-Defamation League (ADL), an organization that tracks hate crimes, is currently organizing a response to the Square assaults.

"If what appears to have happened happened, it's a horrible incident and it's very frightening," said Andrew H. Tarsy, civil rights director of the Massachusetts ADL chapter. "It doesn't matter who you are or what you are... [Hate crimes] should rate everyone's attention."

The ADL is not currently aware of any violent skinhead activity in Cambridge, Tarsy said.

Massachusetts crime statistics show that there were 63 aggravated assaults classified as hate crimes in 1998, the last year for which data is available.