A spike in the number of arrests of juveniles for major felony crimes like assault and rape has some analysts and a City Council member worried about a possible criminal trend among the city’s youth.

The police department arrested 490 more juveniles for major felony crimes in fiscal year 2006 than in fiscal 2005, according to the Mayor’s Management Report. The spike in arrests, about 11.3%, is substantial compared with previous years, which have seen increases of between 1% and 2%. Violent crime is rising across the country, recent FBI statistics show, but New York City has diverged from the trend. While homicides rose by about 3% to 4% in 2005 in America, it dropped by 5.4% in New York City. Major felony crime dropped 6.4% between fiscal 2005 and 2006, the Mayor’s Management Report shows.

The latest data show, however, that the city’s youth population is more in line with the rest of the country.

In addition to the new felony arrests data, the Department of Juvenile Justice saw 721 more youths remain in their system in fiscal 2006 than 2005, the Mayor’s Management Report shows. Attacks by youths on other youths in the department’s care increased to 487 from 350 over the period. Ten more staff members were attacked by youths than in the previous year.

The rise in violence led the department to bring in community-based organizations and a conflict resolution group to work with the staff and youths, a spokesman, Scott Trent, said.

The number of juvenile delinquency filings increased to 9,004 in 2005 from 7,740 in 2004, a spokesman for the Office of Court Administration, David Bookstaver, said.

Analysts agreed that the statistics warranted serious study, but said they aren’t conclusive. An increase in the number of arrests, for instance, could mean the police are targeting youths more or that more youths are committing crimes. The fact that more youths were traveling through the criminal justice system suggests that many of the arrests were being substantiated, analysts said.

“This is the group within which violent criminals are harvested,” a professor at the John Jay College of Criminal Justice, Eugene O’Donnell, said. “If there is going to be any kind of explosion, or detonation of violence in the city, it’s going to come out of that cohort.”

The chairwoman of the council’s Juvenile Justice Committee, Sarah Gonzalez, is planning a hearing in the near future with the police commissioner, Raymond Kelly, and the director of the Department of Juvenile Justice, Neil Hernandez, on the increase in youths involved with major felony crime, a spokesman, Michael Schweinsburg, said.

A senior researcher at the Urban Institute, John Roman, said there were a number of hypotheses being put forward about the rise in violent crime across the country. The country as a whole is spending less money on crime fighting and devoting more resources on preventing terrorism, he said. Also, although there have been targeted efforts against the leaders of gangs in the last few years, law enforcement has forgotten about the average gang member, he said.

“They are less directed, more loosely affiliated,” he said. “What you’re left with is a bunch of motivated people who commit crimes without control.”