The Somali kidnappers of disabled Frenchwoman Marie Dedieu, who died after being snatched from her home in Kenya, are demanding a ransom for the return of her body, France's defence minister said on Thursday.

"The hostage-takers are even trying to sell the remains, it could not be more despicable," French Defence Minister Gerard Longuet told the i-TELE news network.

France said Wednesday that 66-year-old Marie Dedieu, who was kidnapped on October 1 and taken to Somalia, had died in the hands of her captors, most probably because they had refused to provide her medication.

Dedieu had been in a wheelchair and suffering from cancer.

"Seizing a woman of this age, who is sick and paralysed, and not giving her medication, allowing her to develop septicemia from which she apparently died, and then proposing to sell her remains! These are not people who deserve anything but contempt," Longuet said.

He said the French military was not planning any action against the kidnappers in Somalia because they were "a small band, a small minority, an exception who dishonour this territory."

A gang of 10 armed men seized Dedieu from Manda Island in Kenya's Lamu archipelago earlier this month and fled by sea to Somalia, fighting off an attempt by Kenya's navy to stop them.

France has denounced her death as an "an act of unqualified barbarism" and demanded the immediate and unconditional return of her remains.

Kenya has blamed Islamist Shebab rebels in Somalia for a spate of recent kidnappings of foreigners and this week launched an unprecedented incursion into Somalia against the militants.