NEW DELHI (AFP) - India's top court on Thursday (April 28) rejected a French woman's challenge against extradition to Chile, where she is wanted over the assassination of a key supporter of General Augusto Pinochet's military regime.

Chile is seeking the extradition of Marie-Emmanuelle Verhoeven, aged in her mid 50s, for her alleged role in a conspiracy to kill Senator Jaime Guzman Errazuriz on April 1, 1991.

Indian police arrested her on Feb 16 last year as she entered the country overland from Nepal, and she has been held in New Delhi's high security Tihar Jail ever since.

Verhoeven, who has told authorities she was visiting India on a Buddhist pilgrimage, had challenged a treaty between India and Chile allowing for extradition.

Lawyers argued that the treaty dating back to the 1800s was not constitutional because it was not ratified after partition of India in 1947.

But the Supreme Court in a written judgement on Thursday ruled in favour of the Indian government which argued it was still valid, her lawyer Ramni Taneja said.

"This is a big blow and means the extradition proceedings can continue to go ahead. This has been very devastating for her," Taneja told AFP.

Extradition proceedings which had been on hold in another Delhi court are now expected to resume in the coming days, Taneja said.

The Supreme Court in November rejected Verhoeven's request for release on the grounds that her arrest and detention were illegal.

She was arrested in India on the basis of an Interpol notice for her detention issued at Chile's request, but Interpol later cancelled the notice.

The Delhi High Court in September ruled in favour of Verhoeven's immediate release, saying the extradition request was illegal, but shortly afterwards she was re-arrested in prison after a fresh request from Chile.

Verhoeven, a native of Nantes in western Frances, was arrested in the German city of Hamburg in January 2014 and detained for four months.

But Germany rejected Chile's request to extradite her - something her Indian lawyers had pointed to as they tried to thwart her extradition.

Verhoeven lived in Chile from 1985 to 1995 and worked to promote human rights there, before returning to France.

She says she is the victim of a "political vendetta" against her.