Police and Customs officers mounts raids to clamp down on VAT fraud and cigarette smuggling.

Four men from Oxford were among 21 people arrested in a Customs investigation probing a multi-million pound computer parts fraud.

Last night, Operation Darken saw 21 men arrested at business premises and homes in Oxford, Aylesbury, Derby, Nottingham, Birmingham, Leicester, Stevenage and Tring.

The alleged fraud involves firms importing computer components from another European Community country, selling them to another business and charging VAT, then disappearing without paying the tax.

Twelve VAT search warrants were executed and a High Court order freezing 500,000 of suspect assets was also made. Accounts and invoice documents were also seized.

The men were taken to local police stations for questioning and released without charge on police bail. They will be interviewed again at a later date.

Leicester was the centre of the operation, where 12 premises were searched and nine men arrested.

Customs and Excise spokesman Bill O'Leary said: "We are pleased with how Operation Darken went.

"It involved 105 officers and took a great deal of meticulous planning. It is very early in our enquiries and there is still a great deal of work to do."

In the other operation, nearly one million smuggled cigarettes, 62,000 in Oxfordshire, were seized in a three-day customs operation.

Nine teams of HM Customs and Excise officers raided more than 100 addresses, 40 in the county, and seized excise goods on which duty had not been paid.

The total duty evaded is about 250,000. Eight vehicles, four in the county, were also seized.

HM Customs and Excise spokesman Amanda Spencer said: "If you see someone selling smuggled tobacco or alcohol, please call us on Customs Confidential, 0800 59 5000."