Iran has arrested and subsequently deported one of Osama Bin Laden's sons after he crossed the border from Afghanistan or Pakistan.

An Iranian official confirmed a report in London's Financial Times that one of the sons of the al-Qaeda leader had been detained two months ago along with about 20 other people who entered the country and were then "sent back across the border".

He was one of 20 people who were arrested and immediately expelled form Iran around two months ago

Abdollah Ramezanzadeh, government spokesman

"When we arrested those people who illegally entered Iran from our eastern borders, we did not know Bin Laden's son was one of them because they had no identification cards," government spokesman Abdollah Ramezanzadeh.

Osama Bin Laden is believed to have fathered about 20 children - the one alleged to have been in Iran has not been identified.

US intelligence officials have suggested that one of Bin Laden's eldest children, Saad, is now playing a prominent role in his father's network since the group went into hiding following the US campaign in Afghanistan.

Iran has repeatedly denied American accusations that is has harboured members of the al-Qaeda network, which Washington blames for the 11 September attacks on New York and Washington.

But last week Iranian President Mohammad Khatami accused President George Bush of strengthening Osama Bin Laden's stature in the Islamic world.

Mr Bush has branded Iran part of an "axis of evil" together with Iraq and North Korea, accusing it of supporting terrorism.