Khalilzad passed information to Iran

But he denied that these arrests were as a result of information given to Tehran by the United States.

On Tuesday, President Bush's special envoy for Afghanistan, Zalmay Khalilzad, said that Washington had given Iran's foreign ministry details of alleged Iranian interference in Afghanistan and help allegedly given to al-Qaeda fugitives by some groups within Iran.

Safe houses raided

Tehran is not being specific about the number of foreigners under arrest, or their nationalities.

But it is understood that there are tens rather than hundreds of such prisoners, seized mostly during raids on smugglers safe houses in the border province of Sistan Baluchistan.

They are said to include Afghans, Arabs (including Saudi and Kuwaiti nationals) and about seven people who hold European passports.

It is believed that two Kuwaitis have already been handed over to their home government.

A senior Iranian official denied that these people were picked up as a result of information from the United States, or that the arrests were made as a result of US pressure.

US intelligence

He confirmed that Washington had passed on a list of Taleban or al-Qaeda members whom it alleged were in Iran.

But that, he said, had been some months ago.

The official said Iran had followed up this information, but had been unable to locate the people named by the US.

The current group of prisoners had been arrested only recently, both before and after Mr Bush's State of the Union address in which he referred to Iran as being part of an "axis of evil".

They had been under interrogation since then.

None of them were on the list provided by Washington and none appeared on official lists of known al-Qaeda members.

Backgrounds probed

The official said that, although investigations were still continuing into their backgrounds, the majority of these people did not seem to be particularly high ranking or dangerous individuals.

Some may simply have been rank and file Taleban or volunteers who had gone to Afghanistan after 11 September to fight alongside the Taleban.

The official said that some of these prisoners would be handed back to their home governments, particularly those whose countries had existing security agreements with Iran.

Others - including Afghan nationals - would be handed over to Afghanistan's interim administration.

But none would be handed over to the United States, with whom Iran has no diplomatic relations.