(Adds Chadian presidency comment, paragraphs 8-11)

PARIS, July 3 (Reuters) - The hooded killers of the Chadian president's son were filmed on video surveillance cameras in the underground car park in France where his body was found, a judicial source said on Tuesday.

Brahim Deby was discovered dead in his car early on Monday near his home outside Paris. A post-mortem showed he was asphyxiated, probably by powder from a fire extinguisher.

The prosecutor's office in the Paris suburb of Nanterre, which is handling the case, refused to comment on the video images saying the investigation was on-going.

Le Monde newspaper reported that the video showed "several hooded men" attack Deby as he drove into the garage shortly before 7 a.m. (0500 GMT) on Monday.

The paper added that Deby was accompanied by a woman, but that she has not yet been traced.

Chad President Idriss Deby was believed to have wanted his son to succeed him, but this choice was widely unpopular, even by some of his own family, who viewed Brahim as unfit to govern.

The president sacked Brahim as his adviser in June 2006 after the then 27-year-old was arrested in a Paris discotheque for possessing an illegal firearm and drugs. He was given a six-month suspended sentence by a French court.

A Chadian presidency official denied comments by a rebel group fighting a hit-and-run guerrilla war against Deby's forces that Brahim Deby hit ministers during his time as an adviser.

Makaila Nguebla, a Dakar-based spokesman for the rebel Union of Forces for Democracy and Development (UFDD), said on Monday Brahim Deby had been a key source of resentment who drove members of the president's administration to turn against him.

But Dieudonne Djonabaye, assistant director of communications for the Chadian presidency, said: "These declarations are defamatory lies. He never hit a minister or any other figure."

He declined to comment further on the death of Deby's son. (Additional reporting by Pascal Fletcher in Accra)

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