The New York Police Department is planning to double the size of its gang unit to 300 detectives to combat teen violence fueled by dares and insults traded on social media.

Rather than target established street gangs involved in the drug trade, the reinforcements will focus mainly on "looser associations of younger men who identify themselves by the block they live on, or on which side of a housing development they reside," Police Commissioner Raymond Kelly said in prepared remarks.

"Their loyalty is to their friends living in a relatively small area and their rivalries are based not on narcotics trafficking or some other entrepreneurial interest, but simply on local turf," Kelly added. "In other words, `You come in to my backyard and you get hurt. You diss my crew and you pay the price.'"

The remarks were provided in advance of Kelly's appearance Tuesday in San Diego at a gathering of the International Association of Chiefs of Police.

Under the new plan, the NYPD gang unit will work more closely with other divisions that monitor social media for signs of trouble.

Kelly cited a recent case in which investigators used Facebook to track a turf war between two Brooklyn crews named the Very Crispy Gangsters and the Rockstars. The case resulted in dozens of arrests for shootings and other mayhem.

"By capitalizing on the irresistible urge of these suspects to brag about their murderous exploits on Facebook, detectives used social media to draw a virtual map of their criminal activity over the last three years," Kelly said.

Detectives have seen instances where a gang member has taunted rivals by circulating a photo of himself posing in front of their apartment building. Orders of protection also have been posted as a means of intimidation, Kelly said.

The NYPD has developed strict guidelines for investigators using social networks "to instill the proper balance between the investigative potential of social network sites and privacy expectations," Kelly said.

The rules allow officers to adopt aliases for their online work as long as they first get permission from the department. They also will use special laptops that protect their anonymity.

Staffing for the expanded unit will come from gradual redeployment from other areas of the department, not from new hires.