LONDON: The UN’s atomic agency said Iran is carrying out construction activity at a secretive site suspected of being used for nuclear activity, Bloomberg reported on Thursday.

The report comes after President Donald Trump said the United States may attack the site known as Pickaxe Mountain.

International Atomic Energy Agency chief Rafael Grossi said new movement at the complex had been spotted in remote imagery.

“There are some indications that there is movement around this construction site,” Grossi told Bloomberg Television.

“We don’t have any concrete information as to activities that may be taking place there.”

The IAEA’s board on Wednesday reported Iran to the UN Security Council for the first time in 20 years for failure to cooperate in an investigation into uranium traces detected by inspectors at undeclared sites.

Pickaxe Mountain is located just a few kilometers from Iran’s heavily damaged Natanz uranium enrichment facility

The fortified site has two deeply buried tunnel complexes, Reuters reported.

Trump has been threatening strikes on Pickaxe Mountain since at least mid-July, and repeated his warning on Wednesday.

“We notice there’s a little activity at Pickaxe. I would advise Iran not to get cute because we will have to hit them very hard,” Trump said at a the midterm Republican convention.

*With Reuters and AP