"We, as an international community, have questions - open questions - that need to be answered," said Rafael Grossi during a joint press statement with German Foreign Minister Annalena Baerbock in Berlin.
"Our Iranian counterparts still need to provide answers about traces of uranium that were found in places where they should not have been," he added.
Grossi further said the Vienna-based IAEA Board of Governors would meet this week "to analyze the situation" when it comes to Iran's nuclear developments.
Last week, Grossi said Tehran did not offer anything new during a recent meeting in Vienna about its nuclear program, but stressed talks would continue in the coming weeks.
Iran had announced on Nov. 2 that it was sending a delegation to Vienna to try to narrow differences with the IAEA.
Meanwhile, the German foreign minister accused Iran of "systematically violating almost all JCPOA requirements over years."
Baerbock also lambasted Iran for "not complying with other obligations vis-a-vis the IAEA."
Pointing to the security crackdown on pro-freedom protests in Iran, Baerbock said this was the reason why "we must never allow Iran to acquire or buy nuclear arms."
"Iran's nuclear program must be contained in a reliable way and fully monitored with legal but also other agreements," she added.
Tehran is aiming to end the IAEA's investigation of its nuclear activities, among other guarantees, in order to revive the country's 2015 nuclear deal with world powers, commonly known as Joint Comprehensive Plan of Action (JCPOA).
The accord had restricted Iran’s nuclear program in exchange for relief from Western economic sanctions, but former US President Donald Trump withdrew from it in 2018.
Source: Anadolu Agency