VIENNA (AP) -- The UN's nuclear watchdog says Iran has more than tripled its supply of enriched uranium in the last three months and now has more than a ton stockpiled, in violation of the landmark 2015 nuclear deal with world powers.

The International Atomic Energy Agency said in a confidential report distributed to member countries Tuesday that as of Feb. 19, Iran's total enriched uranium stockpile amounted to 1,020.9 kilograms, compared to 372.3 kilograms noted in its last report on Nov. 3, 2019.

The 2015 deal allows Iran only to keep a stockpile of 202.8 kilograms.

"The agency identified a number of questions related to possible undeclared nuclear material and nuclear-related activities at three locations in Iran that had not been declared by Iran," the agency said in a report.

The IAEA had previously said that uranium particles of man-made origin had been discovered at one location outside Tehran that had not been declared, which appeared to confirm allegations made by the U.S. and Israel about a secret nuclear warehouse.

The agency said Tehran responded in a letter on Jan. 28 that "Iran will not recognize any allegation on past activities and does not consider itself obliged to respond to such allegations."

The IAEA responded that its requests for clarification were in line with Iran's broader commitment to allow inspections of its nuclear facilities and not tied in to the landmark nuclear deal with world powers that Iran made in 2015.

Iran has been slowly violating provisions of that deal, known as the Joint Comprehensive Plan of Action, to put pressure on signatories to provide relief from new American sanctions instituted after the U.S. pulled out of the pact unilaterally in 2018.