NEW YORK >> Police deployed extra units to crowded areas of the city and were on heightened alert after scores of people were killed Friday in a series of shootings and bombings in Paris. New York officials said they were acting out of abundance of caution and there were no known threats to the area.

The shootings and explosions at a concert hall hosting an American rock band, a restaurant and elsewhere in Paris marked the deadliest violence to strike France since World War II.

“Every time we see an attack like this, it is not only sobering, it is a reminder to be prepared, to be vigilant, and to make sure that we are reinforcing in places where there would be the greatest likelihood of a potential follow-up attack,” New York City Mayor Bill de Blasio said in an interview with WABC-TV. But the mayor stressed “there are no specific threats directed at New York City that we know of at this time.”

The Police Department said there was “no indication that the attack has any nexus to New York City.” Police officials sent security units to French government locations in the city immediately after the attacks. Heavily armed officers were stationed near the French consulate in Manhattan, and two officers stood guard in front of the door. A small bundle of yellow roses sat on a planter near the door.

The city’s Police Department has detectives from its intelligence division stationed in France. Those detectives are serving as liaisons and will help police in Paris as needed, police said.

“We are monitoring very, very closely the situation with our federal partners and obviously with the folks we have in Paris,” de Blasio said.

Gov. Andrew Cuomo, who ordered state law enforcement officials to remain vigilant after the attacks, said the 408-foot spire atop One World Trade Center would be lit blue, white and red in honor of dozens killed in Paris. Meanwhile, the Empire State Building went dark at 10 p.m. Friday “in sympathy for Paris,” managers of the iconic building tweeted.

“We join them in mourning those who were killed, and in praying for those who were injured or lost loved ones,” he said. “And we continue to stand side by side with them in our commitment to a free and peaceful world.”

Associated Press writers Jake Pearson and Jennifer Peltz contributed to this report.