The 43-year-old Spanish woman was the subject of an international arrest warrant when she was apprehended by Zurich authorities working with Swiss federal police, reported news agencies on Thursday.
Her whereabouts had been unknown since 2007, when she fled Spain after being sentenced by a Spanish court to 11 years in prison – later reduced by the supreme court to six years and nine months – for having acted as a middleman for ETA back in 1998, reported the Spanish press.
The Spanish supreme court judged she had participated in numerous operations staged by the terror group in Europe and South America and had collaborated with central figures in the group, including supplying fake passports.
At the time of her arrest in Switzerland she was carrying false papers prepared by ETA, said the Spanish government.
But on Thursday a Swiss human rights organization working with the Spanish woman told the Swiss press she denied the charges and said they were based on information extracted from her under torture in Spain.
On those grounds she is opposed to her extradition back to Spain.
According to Swiss daily Blick, she claims to have been suffocated with a plastic bag, raped, beaten and subjected to electroshock treatment during five days after her arrest in 1999.
A report from a Spanish prison doctor found injuries consistent with such treatment, it said.
Rolf Zopfi of Augenauf, an NGO founded in 1995 with the aim of uncovering human rights violations, told news agencies that her lawyers now had enough proof to hand over to the Swiss justice office, which will ultimately decide if she should be extradited.
According to European human rights laws a person cannot be extradited if their statements were given under torture.