Stephen Jessel in Paris: The motive is said to be a desire to punish France

The aircraft, a DC-10 operated by the French airline UTA, crashed in Niger in September 1989, killing all 170 people on board.

Debris was scattered over hundreds of kilometres in the Sahara desert.

Sister and son of Laurence Penon, a stewardess killed in the bombing, at the opening of the trial

The Libyans are being tried in absentia after Tripoli refused to hand them over to the French authorities.

The names of the six were twice called out in court to face charges of "murder or complicity in murder connected with terrorism," charges that carry a sentence of life imprisonment.

The trial is expected to last only three days and no defence is being presented. Libya helped France during part of the investigation but did not offer full co-operation.

The prosecution alleges the six accused were working for the Libyan secret service, which is also accused of the bombing of Pan Am 103 over Lockerbie in 1988.

Prosecutors allege a package containing the bomb was planted on a young Congolese with links to Libyan agents in Brazzaville, from where the UTA flight to Paris set off.

It is alleged that Libya orchestrated the attack as part of its territorial war with Chad in the 1970s and 1980s, in which France supported the other side.

French approach

Correspondents have highlighted differences between France's handling of the case and the way the UK and US Governments have sought the extradition of those accused of the Lockerbie bombing.

Pierre Haski: Limited trial which France thinks worthwhile

Evidence against the UTA suspects is said to be much stronger than that against the two Lockerbie suspects.

The six being tried in Paris are said to come from the high echelons of Libya's security apparatus, but if convicted they are unlikely ever to serve prison sentences.

Col Gaddafi in Cairo: Lockerbie, not UTA, on the agenda

The most senior suspect, Colonel Gaddafi's brother-in-law Abdullah Senoussi, is reportedly the deputy head of Libya's security services.

In November it was reported that Mr Senoussi had been tried in Libya and convicted on charges of "dereliction of duty".

Libya did not deny the reports but observers said he was unlikely to serve a reported seven-year sentence given his seniority in the Gaddafi regime.

Correspondents say victim's families and French officials are resigned to the bombers not being brought to justice.

However diplomats are quoted as saying they believe Libya might be prepared to pay damages if the men are convicted.

Limited access

Chief examining magistrate Jean-Louis Brugere was allowed into Libya to question the suspects and Libya provided evidence it said implicated Libya's domestic opposition.

Pierre Haski of the French paper Liberation says it was an explosives-filled suitcase supplied by Libya which led to charges being brought against Mr Senoussi and the others.

Libya has been under UN sanctions since 1992 in connection with the UTA and Pan Am bombs.

The US and UK say they will allow sanctions to be dropped when the Lockerbie suspects are handed over for trial under Scottish law in the Netherlands.