Senior U.N. inspectors arrived in Iran on Monday to push for transparency about its disputed nuclear programme and several European states halted purchases of Iranian oil as part of Western moves to pile pressure on a defiant Tehran.

Iran denies Western accusations that it is covertly seeking the means to build nuclear weapons and has again vowed no nuclear retreat in recent weeks, but also voiced willingness to resume negotiations with world powers without preconditions.

The five-member International Atomic Energy Agency team, led by chief IAEA inspector Herman Nackaerts, planned two days of meetings in another attempt to get answers from Iran regarding intelligence suggesting its declared civilian nuclear energy programme is a facade for researching ways to make atom bombs.

Nackaerts said on departure from Vienna that he wanted concrete results from the talks. His delegation was expected to seek, among other things, to question Iranian nuclear scientists and visit the Parchin military base believed to have been used for high-explosive tests relevant to nuclear warheads.

But Foreign Minister Ali Akbar Salehi dampened speculation about increased IAEA access when he told the student news agency ISNA that the agency officials would not be going to any nuclear sites. No. Their work has just begun, Salehi said.