The four were appearing in front of judges in Paris

The four are under formal investigation for links with terror groups.

Defence lawyers say the four men are in good physical condition but that they are concerned for their psychological state.

The four, all Muslims of North African origin, were picked up by US forces in Afghanistan in late 2001, and sent home on Tuesday from Guantanamo Bay.

About 590 terror suspects are still being held at the American naval base in Cuba.

Little sympathy

The four appeared before judges Jean-Louis Bruguiere and Jean-Francois Ricard after being detained at the headquarters of the French internal security service, the DST.

Mourad Benchellali, Nizar Sassi, Imad Kanouni and Brahim Yadel were placed under investigation on suspicion of associating with a terrorist organisation.

Two of the men - Mr Benchellali and Mr Sassi - are also accused of using false passports in order to travel to Afghanistan.

Their position is one step short of formal charges but it means that Mr Bruguiere, France's top anti-terrorist judge, thinks there is enough evidence against them, gleaned from their interrogation over the last four days, to lead to an eventual court appearance.

GUANTANAMO NUMBERS Estimated 590 terror suspects from about 40 countries held 139 already released 12 "transferred for continued detention" in home countries Four detainees charged

At least two of the suspects were known to the French intelligence services before they reappeared in US detention.

Lawyers for the men wanted the judges to take into account the lengthy captivity they have already served and allow them to go home.

Three other French suspects are still in US custody at Guantanamo Bay.

The Paris government has said it is working to secure their transfer as well.

The case of the seven detainees has failed to arouse much public sympathy in France - although there has been widespread indignation over what many French people see as abuse of prisoners' human rights at the base.