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.
The Police Department said there was "no indication that the attack has any nexus to New York City."
Extra NYPD security was visible outside 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.
NYPD also was keeping an eye on diplomatic outposts and other locations with French connections. Police will participate in a measured show of force in Times Square Saturday afternoon.
Former NYPD Commissioner Ray Kelly on New York security following terror attacks:
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.
Additionally, the MTA has positioned extra officers at Penn Station and Grand Central Terminal. Port Authority police are on heightened alert at all of the agency's bridge, tunnel, rail, World Trade Center and other facilities. Actions include increased patrols and checks of bags, buses, trucks and trains at agency locations. Travelers are reminded to remain vigilant and report any suspicious activities to police or other authorities.
"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 told Eyewitness News.
The mayor said New York City is always evaluating its security measures for attacks like the one in Paris.
Security expert Nick Casale:
"The city is on constant alert, and we're working very, very closely with our federal partners - homeland security, FBI, etc. - so we are ready," de Blasio said.
On Saturday, de Blasio will visit the French Consulate, then he and the French consul general plan to attend a vigil in Washington Square Park to remember the victims of the attacks.
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."
The Metropolitan Opera in New York, in support of and solidarity with France, will perform the France National Anthem before today's 1pm matinee of Tosca. Placido Domingo will conduct the Met Orchestra and Chorus.
In Connecticut, Gov. Dannel Malloy ordered the French flag to fly at the state Capitol and at the governor's residence. "Our thoughts and prayers are with the families who suffered through yesterday's attacks," he said in a statement.
Sporting events with security are wary of the Paris attacks.
The New Jersey Devils are hosting Pittsburgh Saturday at the Prudential Center. The NHL said it has been in touch with teams about heightened security measures.
The Knicks will host New Orleans at noon Sunday at Madison Square Garden. The Rangers also host Toronto at the Garden Sunday.
The Giants are hosting New England Patriots Sunday at MetLife Stadium, East Rutherford. The NFL normally has a high level of security in place.
More on the NYPD's response around New York City:
The Associated Press contributed to this report.