Inspectors suspect the tubes could be related to enrichment of uranium used to make nuclear weapons.

Experts from the UN Monitoring, Verification and Inspection Commission (UNMOVIC) and the IAEA searched 13 sites, Ueki said.

UNMOVIC missile teams visited six sites yesterday al-Amin missile factory in Falluja northwest of Baghdad; al-Mutasim company, south of

Baghdad; the al-Assma company that manufactures the al-Fatah missile parts; the Um al-Marik General Establishment; the al-Kadimia and Al Samoud factories.

A report to the UN Security Council last Friday by chief weapons inspectors Hans Blix and Mohamed El-Baradei said Baghdad was stepping up co-operation with the inspectors.

But Blix also said engine design documents showed Al Samoud missiles could fly around 25 miles over the allowed range of 90 miles.

On Sunday, inspectors tagged several Al Samoud missiles to show they were accounted for and could be tracked.

Yesterday, a UNMOVIC chemical team inspected the al-Muthanna compound in connection with the process of destroying mustard gas and took chemicals for analysis.

A UNMOVIC multi-disciplinary team and a chemical team jointly searched the al-Zahif al-Kabeer centre, a chemical plant located 18 miles northwest of Baghdad. A biological team flew by helicopter to al-Huwijah near the city of Kirkuk, 150 miles north of Baghdad.

An IAEA team conducted radiation surveys in Samaraa area north of Baghdad. Other teams inspected al-Nida and Tho al-Fekar military compounds as well as the Um al-Marik compound also visited by UNMOVIC. Meanwhile, a Mosul-based team inspected the Hadr ammunitions storage facility outside the city 225 miles north of Baghdad.

Iraq this month conceded on three sticking points that won it some credit in Blix's report. It enforced a law banning dealings in weapons of mass destruction or their materials, agreed to interviews with scientists and to surveillance flights over its territory.