Iraq's intelligence operation has uncovered a plot for an attack on subway systems in the United States and Paris, the country's prime minister said Thursday.

Prime Minister Haider al-Abadi said he was told of the plot by Baghdad, and that it was the work of foreign fighters of the Islamic State group in Iraq. Al-Abadi's assertion could not be independently confirmed.

Asked if the attacks were imminent, he said, "I'm not sure." Asked if the attacks had been thwarted, he said, "No." Al-Abadi said the United States had been alerted, and that the suspects included extremists from the United States and France who were fighting for the Islamic State group in Iraq.

"Today, while I'm here I'm receiving accurate reports from Baghdad that there were arrests of a few elements and there were networks from inside Iraq to have attacks ... on metros of Paris and U.S.," al-Abadi said, speaking in English. "They are not Iraqis. Some of them are French, some of them are Americans. But they are in Iraq."

Later Thursday, Deputy Assistant Secretary of State for Iraq and Iran Brett McGurk said in an interview with CNN, "He confirmed to me there is no specific credible threat whatsoever that they have uncovered to the United States. He was discussing in general terms the threat, particularly of foreign fighters and ISIS fighters."

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He made the remarks at a meeting with journalists on the sidelines of a gathering of world leaders at the United Nations General Assembly.

"We have not confirmed such a plot, and would have to review any information from our Iraqi partners before making further determinations," National Security Council spokeswoman Caitlin Hayden said. "We take any threat seriously and always work to corroborate information we receive from our partners. We’re obviously very focused on the issue of foreign fighters, as you saw evidenced yesterday at the Security Council session the President chaired."

"We are aware of the Iraqi Prime Minister's statements and we are in close contact with the FBI and other federal partners as we assess this particular threat stream," New York Police Department Deputy Commissioner of Intelligence and Counterterrorism John Miller said in a statement Thursday. "New York City normally operates at a heightened level of security and we adjust that posture daily based on our evaluation of information as we receive it."

New York Gov. Andrew Cuomo said Thursday his administration is treating the report "with the utmost precaution."

"Our administration has been coordinating at a high level with local, state and federal partners. I want to assure the people of New York that we are monitoring these reports closely and are in close communication with officials in Washington," he said.

The Islamic State extremists' blitz in Iraq and Syria prompted the United State to launch airstrikes in Iraq last month, to aid Kurdish forces who were battling the militants and to protect religious minorities.

In addition to the brutality Islamic State has visited on the people in Iraq and Syria, western leaders have voiced concern that the group would move its terror operations outside the region.

This week, the U.S. and five allied Arab states expanded the aerial campaign into Syria, where the militant group is battling President Bashar Assad's forces as well as Western-backed rebels.

The Associated Press contributed to this report.