The mayor and police commissioner took the subway to a news conference in Manhattan Thursday to reassure New Yorkers they should carry on like normal in the wake of reports of a supposed ISIS threat against U.S. subway systems.

"There is no immediate credible threat to our subway system," said Mayor Bill de Blasio after he and NYPD Commissioner William Bratton emerged from the Union Square subway station. "I say this with confidence. People should go about their businesses as they normally should."

The news conference came hours after Iraqi Prime Minister Haider al-Abadi said he was told of an Islamic State group plot to attack U.S. and Paris subways. Asked whether the attacks were imminent, al-Abadi said, "Yes." Asked whether the attacks had been thwarted, he said, "No." Instead, al-Abadi said the U.S. was alerted about the threat.

At the news conference, Bratton stressed that the plot hasn't been independently verified, but that precautions are in place. "Every precinct was notified immediately," said Bratton, adding that the NYPD brought in emergency services officers and armed police "Hercules Teams." He said he first heard about the plot this morning.

The mayor and police commissioner said commuters shouldn't be alarmed if their bags are checked amid the heightened security.

Separately, New York Gov. Andrew Cuomo and Metropolitan Transportation Authority Chairman Tom Prendergast rode a train from the World Trade Center to Penn Station in Manhattan Thursday afternoon. Cuomo said there was no specific, credible threat to New York City subways.

Millions of people ride New York City subways daily.