WASHINGTON — Increasing violence among teenagers and other youths appears to have contributed to a nationwide crime spike, the Justice Department said yesterday.

Gangs and gun violence are partly to blame for the rise in crime that is on pace to increase for the second straight year, says Attorney General Gonzales in a prepared speech.

In response, the Justice Department is pledging to spend nearly $50 million this year to combat gangs and guns, and will push Congress to enact new laws to let the federal government better investigate and prosecute violent crime.

FBI data from last fall show violent crimes, including murders and robberies, rose by 3.7% nationwide during the first six months of 2006. Those findings came on top of a 2.2% crime hike in 2005 — the first increase since 2001.

Faced with the discouraging data, Mr. Gonzales last fall ordered a study of 18 cities and suburban regions to show why crime is surging. According to Mr. Gonzales’s prepared remarks and a Justice Department fact sheet, obtained by the Associated Press, the study found:

• Many youths have little parental oversight and are too easily influenced by gang membership and glamorized violence in popular culture.

• Loosely organized gangs present the biggest concern for law enforcement officials because they are hard to investigate and their members often commit acts of crime out of self-protection.

• Offenses committed by people using firearms pose a major threat not only to communities, but also to police. So-called “straw purchases,” where gun owners buy their firearms through a go-between is an area of concern.