NEW YORK — Iraq’s prime minister said Thursday that his government had gathered intelligence from captured militants indicating that the Islamic State was planning to attack targets in Europe and the United States, including subways.
US intelligence officials expressed some skepticism about the assertion, pointing out that it was inconsistent with other information they had gathered about the Islamic State. But they were looking into it nonetheless.
The prime minister, Haider al-Abadi, said that the plotting was being carried out by foreign fighters who had joined the Islamic State’s offensive in Iraq.
He said that he had been informed of the information Thursday morning and that Iraq was sharing it with the United States.
“From the details I have received, yes, it looks credible,” Abadi told a group of reporters in New York, where the prime minister and his aides were attending the UN General Assembly meeting.
“Today, while I am here, I am receiving accurate reports from Baghdad,” said Abadi, adding that they came following the “arrest of a few elements.”
“There are networks planning from inside Iraq to have attacks,” he said. “They plan to have attacks on the metros of Paris and the US.”
Caitlin Hayden, spokeswoman for the White House’s National Security Council, said in a statement that it was aware of Abadi’s reported comments.
“We have not confirmed such a plot, and would have to review any information from our Iraqi partners before making further determinations,” she said. “We take any threat seriously and always work to corroborate information we receive from our partners.”
Referring to President Obama’s warnings Wednesday at a special session about foreign fighters of the UN Security Council, Hayden said: “We’re obviously very focused on the issue of foreign fighters.”
FBI officials also reacted to Abadi’s remarks. George Venizelos, the FBI’s assistant director in charge, said in a statement that its agents “are in contact with our law enforcement and intelligence community partners as we assess the validity of this threat.”
Apparently referring to the New York subway system, the country’s largest, Venizelos said, “The FBI Joint Terrorism Task Force, along with the New York City Police Department, remain committed to protecting this city.”
A senior administration official said that nobody in the administration had been aware of such a plot and that it was not raised when US and Iraqi officials met at the United Nations earlier this week.
About 1,000 would-be militants from Asia have moved to Iraq and Syria seeking to join Islamic State, said Admiral Samuel Locklear, commander of US Pacific Command, who spoke at a Bloomberg lunch in Washington Thursday.
It is not clear whether those migrants are now fighting as part of Islamic State or simply have aspirations to do so, Locklear said. Although he said he doesn’t know how Asians are traveling to the Middle East, ‘‘it’s a lot easier to move globally than people think it is.’’
The United States this week bombed targets including the extremist Khorasan Group that the United States believed was plotting an ‘‘imminent’’ attack on the country. The government hasn’t detailed what plot it believes was being planned or shared intelligence about how it knows.
New York City-area transit began increasing security in partnership with New Jersey in the past few weeks, New York Governor Andrew Cuomo said Thursday in an e-mailed statement.
‘‘We are aware of the report and are treating it with the utmost precaution,’’ Cuomo said. ‘‘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.’’
Mass transit has been a popular target for attacks. In 1995, terrorists in Japan released sarin gas in the Tokyo subway system, killing 13 people and injuring dozens. In 2005, suicide bombers targeted the London subway and one of the city’s iconic double-decker buses, killing 52 civilians and injuring about 700.
A naturalized US citizen who had attended an Al Qaeda training camp was convicted in 2012 of planning a thwarted suicide bombing attack on the New York City subway system.
Abadi also said that he had conveyed a message to President Bashar Assad of Syria before the US-led air attacks there that the scope of the bombing would be limited to Islamic State targets and would not extend to targets connected to Assad’s government.
“As a neighbor, I don’t want to be party to the disintegration of Syria or to have diminished sovereignty of Syria,” Abadi said. “So I find it fit to send my adviser to inform the Syria regime this is our vision, this is our aim, they should not misunderstand it.”
Abadi said the Obama administration had informed the Iraqi government that the goal of the airstrikes was not to destabilize the Assad government, and that Iraqi had passed this message to the Syrian government as well.
“We have been given that message by the Americans,” al-Abadi said, “although we just relay a message without any comment.”
The Obama administration has said it has notified Assad’s government of its intention to bomb Islamic militant targets in northern Syria but has said nothing about having offered other assurances to Assad.
A senior administration official would not comment directly on Abadi’s comments regarding Assad. But he said the purpose of the US message to the Assad government was to dissuade it from taking military action to interfere with the bombing.
Material from Bloomberg News was included in this report.