Acting head of the International Atomic Energy Agency (IAEA) Cornel Feruta told journalists in Vienna there had in the past few weeks been "engagement" from Iran on questions relating to its nuclear safeguards declarations to the agency.

He added that "engagement doesn't mean that the issues are completely addressed but it's a step in the right direction."

Feruta said the relevant questions from the IAEA did not touch directly on the faltering 2015 nuclear deal between Iran and world powers but rather on Iran's separate safeguards agreement with the agency.

While the IAEA has been careful not to specify what the outstanding questions relate to, diplomatic sources in Vienna say the agency has been waiting for information from the Iranians relating to samples taken earlier this year from a warehouse near the capital Tehran.

In 2018 Israeli Prime Minister Benjamin Netanyahu accused Iran of using the site for undeclared nuclear activity.

In his remarks to journalists, Feruta did not detail what the agency's questions related to but said the IAEA was "discussing substance" with the Iranians.