A Franco-Algerian nuclear physicist facing terror charges admitted at the start of his trial Thursday to going through a "turbulent" time but denied he intended to carry out attacks in France.

The trial of Adlene Hicheur, who is charged with criminal association as part of a terrorist enterprise, began a week after police shot dead Franco-Algerian Mohamed Merah for killing seven people in and around Toulouse.

French police arrested Hicheur, a researcher studying the universe's birth -- the Big Bang -- at the European Organisation for Nuclear Research (CERN), in October 2009 after intercepting emails he wrote.

The Paris trial was to last two days, with the court to examine 35 emails between Hicheur, 35, and an alleged Al-Qaeda contact.

"I do not contest the fact that I went through a turbulent phase, I have apologised, I cannot say anymore," Hicheur told the court.

He said the emails were the result his "physical and psychological state" while he was on sick leave for a herniated disc.

He said he was just out of the hospital when the emails were written and was taking pain medication.

"I understand that some of the passages may have been uncomfortable or worrying... There was nothing behind it," he said.

Hicheur also denounced the case against him as full of holes.

"I see a lot of confusion and inaccuracies," he told the court. "It would be too tedious to revisit each of them (but) the assertions about me... are inaccurate, are subject to debate."

After more than two years in preliminary detention, Hicheur appeared visibly tired and thin. His father and brothers were in court to support him.

Following Hicheur's arrest at his parents' home near CERN, which lies on the Franco-Swiss border northwest of Geneva, police discovered a trove of Al-Qaeda and Islamist militant literature.

It was "an incredible collection of documents in favour of jihad," prosecutor Guillaume Portenseigne told the court.

But Hicheur told the court police had selectively taken documents from his home.

Investigators "left behind 99 percent of the literature at my home, it's dishonest, it's even disgusting," he said.

"Just because you read something doesn't mean you approve of it," he added.

France's DCRI domestic intelligence agency's suspicions were raised following a statement from Al-Qaeda in the Islamic Maghreb (AQIM) that was sent to President Nicolas Sarkozy's Elysee Palace in early 2008.

Police carried out surveillance on several email accounts including Hicheur's and his exchanges with Mustapha Debchi, an alleged AQIM representative living in Algeria.

In the emails Hicheur proposed "possible objectives in Europe and particularly in France", mentioning for example a French military base at Cran-Gevrier, close to CERN.

Asked by Debchi if he was "prepared to work in a unit becoming active in France," Hicheur replied: "The answer is of course YES".

Magistrates investigating the case said the exchanges "crossed the line of simple debate of political or religious ideas to enter the sphere of terrorist violence."

They say the accused "knowingly agreed with Mustapha Debchi to set up an operational cell ready to carry out terrorist acts in Europe and in France."

The defence is contesting the identity of the alleged Al-Qaeda agent and Hicheur also said police had carried out "dirty work" while translating documents in the case.

If found guilty, Hicheur could be sentenced to 10 years in prison.