Updated

A U.N. human rights expert is calling on Switzerland to reverse its decision to extradite a Basque nationalist to Spain, arguing that her transfer could lead to a conviction based on a confession made under torture.

Nils Melzer, special rapporteur on torture, inhumane and cruel treatment for the U.N. human rights office, says Nekane Txapartegi was convicted in Spain a decade ago for collaboration with the banned Basque separatist group ETA.

The rights office said Tuesday that she took refuge in Switzerland in 2009. Swiss authorities arrested her in Zurich last April following an extradition request from Spain.

It said Spain's civil guard arrested Txapartegi in 1999. Melzer said he had information that she was sexually abused, subjected to electric shock and deprived of sleep, among other abuses, while in detention.