Iran said Monday it independently collected samples at a suspect military site where illicit nuclear work is alleged to have occurred and later handed them to the UN's absent inspectors.

The disclosure that international monitors were not physically present is likely to feed critics of a nuclear deal between Iran and world powers, who have poured scorn on measures used to check if Tehran's atomic programme is peaceful.

In a mark of the high stakes at play it drew a quick reaction from the UN's International Atomic Energy Agency, whose chief insisted that "the integrity of the sampling process and the authenticity of the samples" was not compromised.

The samples were taken under "established procedures", IAEA director general Yukiya Amano said, noting "significant progress" is being made in its long-running probe of whether Iran ever sought to develop a nuclear bomb.

The site at Parchin, east of the capital Tehran, has been at the centre of international scepticism of Iran's activities, specifically that as late as 2003 it carried out work there aimed at developing an atomic weapon.

Iran says accusations from Western intelligence agencies -- including that it conducted explosives tests at Parchin -- are groundless and based on malicious information provided by its enemies.

The sample taking is linked to a so-called roadmap with a December 15 deadline by when the IAEA says ambiguities about past possible military dimensions of Iran's nuclear activities must be resolved.

Much work remains to be done on that report, Amano said.

Iran's environmental sampling from specific parts of the Parchin complex took place in the past week.

"It was done by Iranian experts, in the absence of IAEA inspectors," said Behrouz Kamalvandi, spokesman for Iran's Atomic Energy Organisation.

IAEA and Iranian officials have previously said monitoring can be verified in real time by satellites and sophisticated geolocation technology.

Amano, speaking a day after he visited Tehran and was unexpectedly granted access to Parchin, appeared to reiterate that capability while acknowledging Iran's recent role.

"In the case of Parchin, the Iranian side played a part in the sample-taking process by swiping samples," Amano said in Vienna, adding his experts would analyse them in the coming weeks.

"The agency can confirm the integrity of the sampling process and the authenticity of the samples, which were taken at places of interest to the agency at the particular location in Parchin."

- Entry earlier refused -

He did not name the place, but did say that he and Tero Varjoranta, the IAEA's chief inspector, visited a building previously only monitored by satellite technology, and indicated it had been altered.

"Inside the building, we saw indications of recent renovation work. There was no equipment in the building," he said before appearing to criticise past construction work at Parchin.

"As I have stated in my reports.. the extensive work that has been conducted at the location since early 2012 undermines the agency's ability to conduct effective verification there.

"Our experts will now analyse this information and we will have discussions with Iran in the coming weeks."

Iran had previously refused permission to enter Parchin, highlighting its military function and stressing the IAEA had already conducted inspections in 2005 that yielded nothing.

Iran has said recent work at Parchin was necessary to repair a flood-damaged road.

Reports that international inspectors would not be physically present during sampling were seized on recently by Republicans in the US Congress, who say Iran could cheat the IAEA's monitoring and inspections regime.

On Monday, US State Department spokesman John Kirby would only say of the inspection that "we're comfortable that the process was conducted in accordance with the normal procedures and the agreement that the IAEA had already made with Iran."

The July 14 nuclear deal between Iran and six world powers -- Britain, China, France, Russia and the United States plus Germany -- ended a 13-year standoff over the Islamic republic's nuclear programme.

But the deal cannot go ahead until the accusations about the past possible military dimensions of Iran's nuclear activities are resolved.

Under that agreement Iran, in exchange for the lifting of crippling international sanctions, agreed to curbs on its nuclear programme that experts say would make any dash to produce a weapon all but impossible.

The Republican-led House of Representatives this month rejected the nuclear deal. But it was a purely symbolic vote as one day earlier the Senate cleared the way for the accord to come into force.

IAEA chief heads to Tehran for nuclear talks
Vienna (AFP) Sept 19, 2015 - The head of the UN nuclear watchdog will travel Saturday to Iran for talks on Tehran's nuclear programme with senior officials, the IAEA said in a statement.

The discussions between International Atomic Energy Agency chief Yukiya Amano and the "high-level" officials will take place on Sunday, it said, as a December deadline looms for completion of a long-running investigation into Iran's past nuclear activities.

The IAEA chief was expected to arrive in Tehran in the early hours of Sunday.

"The visit will focus on... clarification of past and present outstanding issues regarding Iran's nuclear programme," it said.

The UN atomic watchdog on September 9 said Iran must resolve some "ambiguities" over its past nuclear activities before crippling international sanctions can be lifted.

The IAEA wants to probe allegations that at least until 2003, Iran's nuclear programme had "possible military dimensions" -- in other words that it conducted research into making a nuclear weapon.

Iran has said that the allegations that it sought to build a bomb -- including that it conducted relevant explosives tests at the Parchin military base -- are groundless and based on faulty intelligence provided by its enemies to a gullible and partial IAEA.

Under an agreement sealed in July between six world powers and Tehran, aimed at ending a 13-year standoff, Iran must dramatically reduce in scale its nuclear activities in order to make any dash to produce atomic weapons all but impossible.

As part of the deal, the IAEA will have to verify that Iran does indeed scale down its facilities, clearing a path towards ending UN, US and EU sanctions.

But the nuclear watchdog is also separately tasked with concluding its decade-old investigation into allegations that at least until 2003, Iran's nuclear programme had "possible military dimensions" -- in other words that it conducted research into how to make an atomic weapon.

Iran signed an agreement with the IAEA on the same July day that it signed the nuclear deal with the six powers setting out a roadmap for wrapping up the investigation by December 15.

During his one-day visit, Amano might also appear in Iran's parliamentary panel tasked with reviewing the nuclear deal -- the Joint Comprehensive Plan of Action, Iranian media reported on Saturday.

Fars news agency quoted conservative lawmaker Alireza Zakani, who leads the panel, saying that Amano will go to the parliament at 2:00 PM local time (0930 GMT) on Sunday.

Iranian lawmakers are in the final steps reviewing the text. It is not clear whether there will be a vote or not.

Earlier this month the Republican-led US House of Representatives rejected the deal on Iran's nuclear program, in a purely symbolic vote held a day after the Senate cleared the way for the accord to come into force.

Dutch FM to visit Iran
The Hague (AFP) Sept 19, 2015 - Holland's Foreign Minister Bert Koenders will travel to Iran on Sunday for a two-day visit -- the first by a top Dutch diplomat for some 14 years.

Koenders trip, announced Saturday by the foreign ministry, follows hot on the heels of other European ministers keen to restore links with Tehran in the wake of the historic July nuclear accord struck between the Islamic Republic and global powers.

"It's the first time in 14 years that a Dutch foreign minister is visiting Iran," the ministry said in a statement saying Koenders' trip would take place on Sunday and Monday.

He will meet Iranian counterpart Mohammad Javad Zarif and Iranian President Hassan Rouhani for talks on implementing the nuclear deal, under which Iran will sharply curtail its nuclear programme in return for a gradual lifting of economic sanctions.

They will also discuss trade links, human rights and Iran's role in the upheavals in the Middle East.

Koenders said he hoped to give "fresh impetus" to his country's ties with Iran and provide "greater opportunity to talk constructively with each other."

French Foreign Minister Laurent Fabius -- one of the main negotiators of the deal reached in Vienna on July 14 -- has already visited Tehran, as have British Foreign Secretary Philip Hammond and EU foreign policy chief Federica Mogherini.

Other European visitors to Iran -- which has had frozen ties with much of the outside world for the past decade or so due to its suspect nuclear programme -- include Austrian President Heinz Fischer and German Vice Chancellor Sigmar Gabriel.

The easing of international sanctions on Iran following the deal struck with the so-called P5+1 group -- Britain, China, France, Germany, Russia and the United States -- will unlock a flow of investment to the Islamic Republic.

The economy of the oil-rich nation of 80 million people has been severely hit by the sanctions.