The former Central Intelligence Agency (CIA) station chief in Milan who was detained in Panama on Italy's request is on his way back to the United States, the US State Department has said.

"It's my understanding that he is in fact either en route or back in the United States," spokeswoman Marie Harf told reporters on Friday when asked about the whereabouts of the officer.

But she gave no further details about the case which has been shrouded in secrecy.

The American spy, Bob Seldon Lady, was convicted in absentia along with 22 other CIA agents in 2009 by Italian authorities over the kidnapping of an Egyptian imam.

The imam, Osama Mustafa Hassan, a ultra-conservative Islamic opposition figure better known as Abu Omar, was snatched from a street in Milan in 2003 in an operation co-ordinated by the US spy service and the Italian military intelligence agency SISMI.

'Extraordinary rendition'

The Italian justice ministry announced Lady's detention in Panama on Thursday but it was unclear when he was taken into custody or whether he remained a CIA employee.

The former head of the CIA station in Milan, now 59, received the heaviest sentence, which was increased from eight to nine years on appeal in 2010.

The case was one of the world's biggest to take aim at Washington's controversial "extraordinary rendition" programme, which was set up in the wake of the September 11, 2001 attacks to capture and interrogate suspected terrorists.

Under the programme, suspects were transported back to their home countries that were often known to use torture.

The United States has said little about the case and refused to extradite the CIA officers.

When asked about the latest developments in the case, the CIA declined to comment on Friday.

Source: Agencies