Security at Long Island train stations, New York City subways and other “areas of concern” was beefed up following Friday’s subway bombing in London.

Authorities saw no credible evidence of any imminent threat locally but acted as the Islamic State claimed responsibility and London authorities warned of more, imminent attacks.

“Out of an abundance of caution, I am directing state law enforcement to increase security at vital assets across New York, including airports, bridges, tunnels and mass transit systems,” Gov. Andrew M. Cuomo said in a statement.

The Suffolk County Police Department said it was stepping up patrols around Long Island Rail Road stations.

“Attacks against transit systems are designed to cause fear among those who utilize them,” department officials said in a statement.

“Our department’s increased presence at LIRR stations in Suffolk County is meant to reassure commuters that they are safe and that they should go about their lives without fear, yet remain vigilant and immediately report any observed suspicious behavior to law enforcement,” the statement said.

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Nassau County police said they would “continue to intensify their patrols in all areas of concern.” Officials reminded the public that suspicious social media activity may be reported through Text-A-Tip on the Nassau County Crime Stoppers’ free app.

In New York City, police made its presence visibile by moving extra officers, heavy weapons teams and bomb-detection dogs into the transit system.

NYPD Commissioner James O’Neill said in a tweet that there was no direct threat to New York City, and he urged residents to “always remain vigilant.”

Friday morning, Veronique Hakim, managing director of the Metropolitan Transportation Authority, had said the agency’s security forces wer “all out this morning en masse.”

A homemade bomb exploded on a packed London subway train during rush hour, leaving 22 people injured but no one seriously hurt, The Associated Press reported.

Commuters reported a noise and a flash aboard the District Line train at Parsons Green stationy, followed by chaos as hundreds of people rushed away.

Mark Rowley, head of counterterrorism for the Metropolitan Police, said “we now assess this was a detonation of an improvised explosive device.” Photos taken inside the train show a white plastic bucket inside a foil-lined shopping bag.

With Alfonso A. Castillo and Ellen Yan