New York Beefs Up Police Presence Due to Bombing, UN General Assembly Meeting

Both the city and state are increasing numbers of officers on the ground.

"Out of an abundance of caution, we are increasing security at high-profile locations across the city, and all state agencies continue to remain on alert," Cuomo said in a statement.

But Kelly cautioned, "You don't have an inexhaustible group of people to help," secure the city.

He said law enforcement typically handles such a complex security efforts by breaking them into tiers, and that some members attending the General Assembly meeting may be considered to require more protection than others. He used Secretary of State John Kerry as an example of the type of figure who would receive the highest level of security, and said that it would likely be the NYPD's job to ensure that hotels at which UN members stay and events at which they are expected to attend are well-secured.

Kelly said law enforcement will be looking for tips from the public, a point echoed by the mayor.

"Be vigilant at this point in time," de Blasio said. "Not just because of this incident: Be vigilant because we're going into the United Nations Assembly week. Be vigilant because the police need your help. And if you see anything that might be pertinent to this case, we need you to call it in."