NEW YORK — A confidential report from the U.N. nuclear agency says Iran has rapidly ramped up its nuclear activities in recent months.

In a report Friday by the International Atomic Energy Agency, the watchdog group said that Iran has upgraded production of enriched uranium over the last four months and has failed to give a convincing explanation about missing uranium metal, the Associated Press reported.

Iran has repeatedly insisted that its nuclear activities are for peaceful purposes, though most Western governments dispute that. The IAEA report expressed “serious concerns regarding possible military dimensions to Iran’s nuclear program.”

The report comes just two days after IAEA officials returned from a failed effort to persuade Iran to cooperate with international inspections.