Iran is further expanding its nuclear capacities, the International Atomic Energy Agency said Thursday, one week after the agency's board of governors passed a resolution criticising Tehran's lack of cooperation with the UN nuclear watchdog.

The IAEA informed its members that Tehran told the agency it was installing more cascades at the enrichment facilities in Natanz and Fordow, according to a statement sent to AFP.

A cascade is a series of centrifuges, machines used in the process of enriching uranium. A diplomatic source deemed this development as "moderate".

The motion brought by Britain, France and Germany -- but opposed by China and Russia -- at the IAEA's 35-nation board last week was the first of its kind since November 2022.

The resolution -- which Tehran slammed as "hasty and unwise" -- came amid an impasse over Iran's escalating nuclear activities and as Western powers fear Tehran may be seeking to develop a nuclear weapon, a claim Iran denies.

Although symbolic in nature at this stage, the censure motion aims to raise diplomatic pressure on Iran, with the option to potentially refer the issue to the UN Security Council.

In the past, similar resolutions have prompted Tehran to retaliate by removing surveillance cameras and other equipment from its nuclear facilities and ratcheting up its uranium enrichment activities.

"The report issued today by the IAEA makes clear that Iran aims to continue expanding its nuclear programme in ways that have no credible peaceful purpose," US State Department spokesman Matthew Miller said in a statement.

"Iran must cooperate with the IAEA without further delay to fully implement its legally binding safeguards obligations."

According to the IAEA, Iran is the only non-nuclear weapon state to enrich uranium to the high level of 60 percent -- just short of weapons-grade -- while it keeps accumulating large uranium stockpiles.

The IAEA has said that Tehran has significantly ramped up its nuclear programme and now has enough material to build several atomic bombs.

The Islamic republic has gradually broken away from its commitments under the nuclear deal it struck with world powers in 2015.

The landmark deal provided Iran with relief from Western sanctions in exchange for curbs on its atomic programme, but it fell apart after the unilateral withdrawal of the United States under then-president Donald Trump in 2018.

Efforts to revive the deal have so far failed.