Vienna, Aug 29 (DPA) The International Atomic Energy Agency (IAEA) increased its pressure on Iran to prove it had not done work related to nuclear weapons, in a report published Friday that confirmed a slight decrease in the country's enrichment activities.

In his latest report, IAEA chief Mohamed ElBaradei also said Iran had partly improved its cooperation with the Vienna-based agency by allowing better monitoring at its controversial enrichment facility in Natanz, and by granting a visit to a research reactor that is under construction.

The report came as the September deadline set by the United States to pressure Iran into agreeing to nuclear talks draws close and Western countries are set to consider new sanctions.

It remained to be seen whether Tehran's partial increased transparency would last, a senior official close to the IAEA said.

Whether Iran allows a further visit to the Arak reactor 'will be the proof of the pudding,' he said.

Regarding the weapons studies, IAEA inspectors have received intelligence information from a number of countries they consider 'generally consistent', which includes indications Iran has worked on detonators and the modification of a missile which could be related to a nuclear warhead.

ElBaradei's report made clear that although Iran publicly claims that these intelligence documents are forgeries, it has acknowledged some of this work but says it was not related to building an atomic bomb.

'So there is a real basis in the documentation,' the senior official said.

'In the light of the above, the agency has repeatedly informed Iran that it does not consider that Iran has adequately addressed the substance of the issues (...),' ElBaradei concluded in the report issued to all IAEA member states.

Concerning uranium enrichment, the IAEA said some 4,600 centrifuges were operating in Natanz on August 12, 300 fewer than reported in the previous June report.

Officials gave no explanation about this first such decrease in three years.