Federal officials have warned the NYPD to be on alert for the possibility of retaliation attacks after an American soldier is suspected of killing 16 Afghan civilians last week.

The Department of Homeland Security bulletin warned that the alleged rampage could be "incorporated into violent extremist propaganda and could contribute to an individual's radicalization to violence."

The NYPD said its counterterrorism plan is "informed by events overseas, including Afghanistan," but stressed that there is no specific threat to New York City.

Police Commissioner Ray Kelly told NBC New York on Friday that the NYPD is "concerned about what did happen in Afghanistan."

"But we're on alert all the time in this city," he added. "We feel we have to be. We are the No. 1 terrorist target in this country certainly. So we have a lot of additional safeguards in place but clearly the horrific events in the last week or so in Afghanistan has been a matter of concern for us."