Mr Bongo's lawyers had said on Tuesday that the ousted president and his two youngest sons had gone on hunger strike to protest against the alleged torture, which they said included beatings, whippings, strangulation and electrocution with a taser.
They added that they had filed a complaint with the Paris judicial court over the alleged acts.

Speaking in an address on state TV, government spokeswoman Laurence Ndong said the allegations were "slanderous" and "damaging Gabon's image".
"The government wishes to state emphatically that they are not being subjected to any form of torture or mistreatment as stated by their lawyers," she added.
She further denied that the junta authorities were preventing Mr Bongo from leaving Gabon or receiving visitors, including his lawyers and family members, at his home.

Bongo, 65, was ousted in a military coup in August last year, shortly after he won a disputed presidential poll.
He had led the oil-rich country since 2009 when he succeeded his father who had been in power for more than 40 years.