The first criminal trial over the CIA's "extraordinary rendition" of terror suspects has opened in Italy.

Twenty-six Americans and six Italians are accused of kidnapping an Egyptian terror suspect and sending him to Egypt, where he was allegedly tortured.

The Americans - most believed to be CIA agents - will be tried in absentia. Italy has not announced if it will seek their extradition to the Milan trial.

US President George W Bush will arrive in Italy hours after the trial opens.

Meanwhile, the head of a European investigation into the rendition process is due to present more findings on Friday.

Surprise witness

This is a controversial trial and it made a stuttering start, says the BBC's Christian Fraser in Rome.

In their opening submissions this morning, defense lawyers called for proceedings to go behind closed doors, but the judge rejected their request.

The defense team is supported by the Italian government which has asked the country's highest court to set aside the rendition trial, saying prosecution documents will break state secrecy laws and damage relations with the CIA.

The Constitutional Court is due to rule on that appeal by September, and defense lawyers are expected to ask that the trial be adjourned until the high court makes its ruling.

Hassan Mustafa Osama Nasr - also known as Abu Omar - was snatched from a Milan street in February 2003.

Italian prosecutors say Nasr was taken to US bases in Italy and Germany before being taken to the Egyptian capital of Cairo. Nasr says he was tortured during his four-year imprisonment in Cairo.

At the time of his arrest he was suspected of recruiting fighters for Islamic groups but had not been charged.

He was released by Egypt earlier this year, his lawyer said.

A senior US official has said that the 26 Americans accused of Nasr's kidnapping would not be sent to Italy even if Rome made an extradition request.

One of the surprise witnesses in the case will be Philip Morse - one of the minority owners of the US baseball team the Boston Red Sox, says our Rome correspondent.

It is alleged that his Gulfstream jet was used by the CIA to fly Abu Omar out of Italy, our correspondent says.

'Web of abuse'

Also on Friday, Swiss senator Dick Marty, leading an inquiry on behalf of the Council of Europe, is due to release more of his findings.

Last year, he accused 14 European nations of colluding with US intelligence in a "spider's web" of human rights abuses, and specified Romania and Poland as suspected locations for CIA "black sites", where terror suspects are secretly held.

President Bush acknowledged the existence of such centers last year, but did not say where they were.

Mr Bush will arrive on Friday for talks with Pope Benedict XVI and Italian Prime Minister Romano Prodi.

Mr Prodi has already said that the extraordinary rendition case will not be on the agenda.

PHOTO CAPTION

Hassan Mustafa Osama Nasr