CAIRO (Reuters) - Egypt's state-appointed human rights council has urged prosecutors to investigate whether an economic researcher who authorities say died after being interned in a psychiatric hospital was a victim of forced disappearance.

       The National Council for Human Rights (NCHR) also said in a statement posted late on Monday that it was awaiting the result of an autopsy of the economist, Ayman Hadhoud, to see if he was subjected to torture before his death.

       Forced disappearance is a term commonly used for detentions carried out by security agencies during which lawyers and relatives are not officially informed about the whereabouts of detainees or the charges against them.

       Hadhoud was an economist and member of the Reform and Development Party, whose leader, Mohamed Anwar al-Sadat, sits on the NCHR and has mediated some recent prisoner releases.

       Egypt's public prosecution said in a statement that police arrested Hadhoud on Feb. 6 after a guard found him trying to enter an apartment in Cairo's Zamalek neighbourhood, and that prosecutors sent him to a mental health hospital after judging him "incomprehensible" during interrogation.

       The prosecution said it was notified of his death from cardiac arrest on March 5.

       Hadhoud's brother has been quoted by local media raising concerns about the case, saying the family were only informed of his death last week and that an autopsy was not ordered until Sunday.

       Two security sources, speaking on condition of anonymity, said Hadhoud had been detained in February on accusations of spreading false news, joining a banned group and disturbing the public peace, charges often levelled at political dissidents and activists.

       There has been a far-reaching crackdown on political dissent in Egypt since then-army chief Abdel Fattah al-Sisi led the overthrow of democratically elected president Mohamed Mursi in 2013.

       Rights groups say tens of thousands have been detained and many have been denied due process or been subjected to abuse or poor prison conditions. Officials say security measures were needed to stabilise Egypt, deny the existence of political prisoners, and assert that the judiciary is independent.

       The NCHR said it was coordinating with the public prosecution and interior ministry over 19 complaints it had received about alleged cases of forced disappearance since it was reconstituted late last year, as well as complaints about extended pre-trial detention and inhumane treatment in prisons.

       The revival of the NCHR, which had been in abeyance for several years, is one of a series of steps Egyptian authorities have taken in recent months in what they say is an effort to address human rights. Critics have dismissed those efforts as hollow.

       (Reporting by Cairo bureau, Editing by William Maclean)