"We are at any given time very engaged in, stay aware of potential threats and individuals, et cetera, in the city," Bratton stated. "As we gather more intelligence, we certainly ramped up that activity, as it relates to those that we have concerns with."
Bratton noted that the NYPD has already planned a trip by its representatives to Belgium and France as a follow up to address previous terrorist incidents, and underscored the timeliness of the previously scheduled visits.
He also pointed out the NYPD will add a detective to the European Union's law enforcement agency Europol to aid in its operations.
"We are in the process of adding another detective to Europol to deal with many of the issues that they are dealing with," Bratton added.
Earlier on Tuesday, a series of blasts hit Brussels' Zaventem airport and the city’s central metro station, killing at least 34 people and injuring more than 150 others.