The NYPD is vigilant and prepared in the face of heightened terrorism concerns abroad fanned by the growing influence of the Islamic State, Police Commissioner William Bratton said Friday.

Bratton made the statement -- stressing there is no specific threat to the city -- shortly after British Prime Minister David Cameron announced that his country's terror threat level had been raised to "severe."

The elevated security level in Britain means a terrorist attack on the country is "highly likely," but officials in the United States haven't taken a similar posture.

Bratton said the NYPD counterterrorism apparatus is in close touch with federal agencies and suggested the department has tracked at least one New Yorker who may have traveled to the Mideast to get involved in the fighting there.

"The NYPD is following developments in the U.K. closely and working with the FBI Joint Terrorism Task Force to monitor any developments," he said in a statement. "As of now, there is no specific credible threat to New York City."

"Everybody is taking precautions, which is the right thing to do," said security consultant Robert Strang of Manhattan.

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Rep. Peter King (R-Seaford) said law enforcement in the city is on high alert. "As far as New York City is concerned, New York City is at the highest threat level," he said.

Port Authority officials couldn't be reached for comment on the security concerns.

With two major public events underway in the city over the Labor Day weekend -- the West Indian Day Parade and the U.S. Open -- officers will be out in force around the five boroughs in multiple layers of security, which include heavily armed Hercules units, special mobile watchtowers and dozens of critical response vehicles, officials said.

In a briefing with reporters Thursday, Bratton said events in the Mideast were of great concern and he would be proposing to Mayor Bill de Blasio that the city create a special critical response vehicle unit instead of having to borrow vehicles and officers from individual precincts. The response vehicles are deployed around important buildings and venues as a counterterrorism measure.

King said the Islamic State is a much more serious threat than al-Qaida and that it has been able to draw roughly 100 fighters from the United States. He believes the terror group wants to launch attacks on this country.

Bratton on Thursday wouldn't say if the NYPD was looking into a report that a Brooklyn man has tried to link up with terror groups in the Mideast.

A law enforcement source who didn't want to be named said the department had heard that the man had traveled to Syria to train foreign fighters with the Free Syrian Army, which opposes the regime of Bashar Assad, but had later returned to his native Yemen.

Investigators were also looking into whether Middle Eastern drug gangs in New York City have been sending money raised from the sale of khat, a plant used as a stimulant drug, to fund terror groups, the source said.