"The significantly increased production and accumulation of highly enriched uranium by Iran, the only non-nuclear weapons state producing such nuclear material, is seriously alarming, writes the IAEA in a report that several media outlets have taken part of.
The information comes at a sensitive time when Iran and the USA have had several rounds of talks in recent weeks in an attempt to agree on a new agreement.
The IAEA's report shows that Iran has built up a stockpile of 408.6 kilos of uranium enriched to 60 percent.
This is an increase of 133.8 kilos – equivalent to nearly 50 percent – since the IAEA's last report in February, when Iran had 274.8 kilos.
"Not peaceful"
Israel's Prime Minister Benjamin Netanyahu says in a statement that the report makes it clear that Iran is "determined to complete its nuclear weapons program".
"The purpose of Iran's nuclear energy program is not peaceful", says Netanyahu.
"The international community must act now to stop Iran."
Iran denies that the country wants to develop nuclear weapons, instead claiming that the purpose of the nuclear energy program is only peaceful.
In a reaction to the report says the Iranian Foreign Ministry in a statement that the report was "prepared for political reasons", is "unbalanced" and lacks a "correct assessment" of the situation.
American intelligence services estimate that Iran has not yet developed a nuclear weapons program, but has positioned itself to start one if it wanted to.
42 kilos are enough
Uranium enriched to 60 percent is a relatively short technical step from the level required for nuclear weapons – 90 percent. Approximately 42 kilos of uranium are theoretically enough to build an atomic bomb, if enriched to 90 percent, according to the IAEA.
Total, Iran's stockpile of enriched uranium consists of over 9.2 tons. This includes uranium enriched to lower levels as well.
In a second separate report from the IAEA, Iran is criticized for not cooperating sufficiently, not least when it comes to traces of nuclear material found at certain facilities.
IAEA chief Rafael Mariano Grossi urges Iran on Saturday to "cooperate fully".
Iran and the USA have been holding nuclear energy talks since April 12. This is the highest level of negotiations between the countries since a previous agreement between Iran and the Western world from 2015 collapsed in 2018, during President Donald Trump's first term.
