In a letter to the UN Security Council, the head of the International Atomic Energy Agency (IAEA) also said satellite imagery revealed that at least one site where contaminated rubble from Iraq's defunct nuclear programme had been buried had been extensively excavated.
IAEA Director General Muhammad al-Baradai said these assessments "need to be followed up through verification in Iraq in order for the agency to draw conclusions." Getting UN nuclear inspectors back into Iraq, however, remains problematic.
IAEA inspectors left Iraq just before the March 2003 US-led war, along with inspectors searching for biological and chemical weapons. The Bush administration then barred all UN inspectors from returning, deploying US teams instead in what turned out to be an unsuccessful search for Iraqi weapons of mass destruction.
Nonetheless, IAEA teams were allowed into Iraq in June 2003 to investigate reports of widespread looting of storage rooms at the main nuclear complex at Tuwaitha, and in August 2004 to take an inventory of several tons of natural uranium in storage near Tuwaitha.
The UN watchdog is concerned
over the protection of Iraqi sites
Last month, Security Council members said after a closed-door discussion that the time to start examining the future of UN weapons inspectors is getting closer.
No timetable has been set, though China's UN Ambassador Wang Guangya said recently he expected the issue to be taken up in the next several months.
The Iraqi government has been waging a public campaign to stop using Iraqi oil revenue to pay the UN weapons inspectors, calling them "irrelevant" and costly.
Al-Baradai's six-month report to the council said IAEA inspectors are ready to resume verification in Iraq if directed by the council, and made clear that there are many sites to look at.
Since 2003, al-Baradai said, the IAEA has analysed satellite imagery of 141 of the 175 locations it previously identified as primary sites that contributed to Iraq's clandestine nuclear programme, which was halted in the mid-1990s.
Analysts were looking for changes in the infrastructure of the sites, he said.
"This assessment has revealed significant dismantling and removal activities at 37 of the most capable sites since March 2003"
"This assessment has revealed significant dismantling and removal activities at 37 of the most capable sites since March 2003," al-Baradai said, without giving any details.
At the request of the Iraqi authorities, al-Baradai said the IAEA has compiled information to assist Iraq in planning future clean-up activities, based on its knowledge of certain facilities and other relevant locations.
In late October, al-Baradai released an Iraqi report on the disappearance of 377 tons of high explosives from the al-Qaqa site south of Baghdad, including HMX which can be used to ignite a nuclear weapon. The missing explosives became a heated issue in the final days of the US presidential campaign.
Investigations were promised, but al-Baradai said in Friday's report that to date, the IAEA had received no additional information that could shed light on this matter.