Prime Minister Benjamin Netanyahu of Israel told the United Nations on Thursday that his intelligence agents had discovered a “secret atomic warehouse” in downtown Tehran, escalating a growing confrontation with Iran and setting up a direct challenge to its government to open the facility to inspectors and prove it is not in violation of the 2015 nuclear deal.

Mr. Netanyahu’s claim, made at the same podium at the General Assembly where in past years he argued vociferously against signing the nuclear accord with Iran, came with photographs and map coordinates of the facility. He described it as a warehouse only three miles from the one that Israeli agents broke into last January, making off with 50,000 pages of documents and computer discs full of atomic weapons, warhead designs and production plans.

“Today, I am disclosing for the first time that Iran has another secret facility in Tehran,” Mr. Netanyahu said. “A secret atomic warehouse for storing massive amounts of equipment and material from Iran’s secret nuclear weapons program.”

Mr. Netanyahu did not describe what kind “equipment and material” was contained in the warehouse. Some types of equipment, especially if it was dismantled or could be put to a variety of industrial uses, may be permissible under the terms of the accord.