The wife of former Nissan boss Carlos Ghosn has said he is suffering under "harsh treatment" in a Japanese jail, where he has been detained for nearly two months, BBC reports.
In a letter to Human Rights Watch, Carole Ghosn described constant interrogations and appealed for action.
Mr Ghosn's arrest for financial misconduct shocked the auto industry.
His detention, which is likely to continue for months, has drawn criticism of Japan's justice system.
In Japan, suspects can be held while prosecutors investigate allegations. They can also be detained for long periods once charges have been filed.
Mr Ghosn, a towering figure of the car industry, faces three charges of financial misconduct including understating his income and aggravated breach of trust.