The decision is an extraordinary gain in establishing responsibility for human rights abuses

Jose Miguel Vivanco, Human Rights Watch

Foreign Minister Jorge Castaneda said he had made the decision based on Spain's request and last month's recommendation by a Mexican court that Mr Cavallo be extradited.

Lawyers for Mr Cavallo - who is currently being held in a Mexican prison - say they will launch an appeal against the decision within the 15-day legal limit.

International human rights group Human Rights Watch backed the decision, calling it "an extraordinary gain in establishing responsibility for human rights abuses."

"It also marks a drastic change in Mexico's foreign policy," said the director of the group's Americas section Jose Miguel Vivanco, referring to Mexico's previous refusal to allow extradition of foreigners.

'No evidence'

A former lieutenant in the Argentine navy, Miguel Ricardo Cavallo is accused of committing crimes of genocide, terrorism and torture against left-wing opponents of Argentina's former military rulers in the 1970s and 1980s.

Only a few graves of the 'disappeared' exist

But according to Mr Cavallo's lawyer Alvaro Carrillo: "There is no evidence to prove the crimes he is being charged with, nor his participation."

Leading the investigation of Mr Cavallo is Spanish judge Baltasar Garzon, who last year attempted to extradite Chile's former military ruler General Augusto Pinochet.

Human rights groups estimate that about 30,000 people were killed or "disappeared" in the Argentine military's war against left-wing guerrillas and their sympathisers.

Many were tortured, drugged and thrown from aircraft into the River Plate or Atlantic Ocean.

Question of identity

Mr Cavallo was originally arrested last August in the Mexican resort of Cancun after a newspaper accused him of being a former intelligence agent who used the alias "Serpico".

Mr Cavallo says he is simply a retired soldier

Under this name, he allegedly ran the notorious Navy School of Mechanics in Buenos Aires, where many opponents of the military regime were imprisoned.

However, Mr Cavallo says he has been the victim of mistaken identity and that he is, in fact, a retired member of the Argentine marines.