Mr Sharafi (L) with Foreign Minister Mottaki on arrival back in Iran

Jalal Sharafi, the second secretary at Iran's embassy in Baghdad, told Iranian media the agents had interrogated him on his country's role in Iraq.

Mr Sharafi said he had been taken from his car by men in Iraqi army uniforms.

The White House said the US had not been involved in his detention, and it welcomed Mr Sharafi's return to Iran.

Irbil detentions

Mr Sharafi told the Irna state news agency he was subjected to torture "day and night".

"I was kidnapped on a Baghdad street while shopping by officials who had Iraqi defence ministry ID cards and were riding in American forces vehicles," he said.

This is just the latest theatrics of a government trying to deflect attention away from its own unacceptable actions

Gordon Johndroe

White House spokesman

Mr Sharafi said he was taken from the Karrada district to a base near Baghdad airport and questioned in Arabic and English.

"The CIA officials' questions focused mainly on Iran's presence and influence in Iraq," he said.

"When faced with my responses on Iran's official ties with the Iraqi government they increased the torture."

Iran's Fars news agency said: "He showed reporters the marks left by torture on his body that are now being treated by doctors."

White House spokesman Gordon Johndroe, accompanying President George W Bush in Texas on Saturday, denied any coalition role in the case.

"The United States had nothing to do with Mr Sharafi's detention and we welcome his return to Iran.

"This is just the latest theatrics of a government trying to deflect attention away from its own unacceptable actions," he said.

Iraqi Foreign Minister Hoshiyar Zebari said Baghdad did not know who had held him.

Diplomatic tension remains high between Washington and Tehran over the detention by US forces of five Iranians in the Iraqi city of Irbil in January.

The US suspects them of aiding the Iraqi insurgency. Tehran says they have diplomatic status.

Iran this week released 15 UK sailors it had held for 13 days.