Spain's high court in November approved the extradition of Alexander Pavlov, who was head of security for Mukhtar Ablyazov, a prominent Kazakh opposition leader and businessman.
"All countries must ensure that extradition does not put an individual at risk of persecution, torture, inhuman or degrading treatment," Juan E. Mendez, the U.N's special rapporteur on torture, said in a statement from the Office of the High Commissioner for Human Rights. "Spain must adopt all necessary measures to safeguard Mr. Pavlov's rights and physical integrity."
Pavlov was detained by Spanish authorities in 2012 on an Interpol warrant requested by Kazakhstan. He is accused of financial and terrorism-related crimes.
Mendez's comments were echoed by Francois Crepeau, special rapporteur on the human rights of migrants, who said the rights of foreigners were no less important than those of a country's citizens.
"The question we should ask ourselves is: would we as confidently send a citizen to the same fate?," Crepeau said.
The court's decision to extradite Pavlov must be approved by Spain's Council of Ministers.