UPDATE — 7:30 p.m. ET: Deputy national security adviser Ben Rhodes said aboard Air Force One the U.S. has "not confirmed any specific threat against the United States."
The State Department added that the Iraqi prime minister later said there is no specific threat and that he was speaking generally.
NEW YORK (AP) -- Iraq's prime minister said Thursday his country's intelligence operation has uncovered a plot for an attack on subway systems in the United States and Paris.
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. There was no immediate comment from Washington or Paris, and al-Abadi's assertion could not be independently confirmed.
US President Barack Obama and Iraqi Prime Minister Haider al-Abadi meet during the United Nations General Assembly at the United Nations in New York, September 24, 2014. SAUL LOEB/AFP/Getty Images
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."
He made the remarks at a meeting with journalists on the sidelines of a gathering of world leaders at the United Nations General Assembly.
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.