By Dan Collyns BBC News, Lima

Santiago Martin Rivas made a dramatic about-turn in his evidence

An ex-army officer accused of running a death squad in the 1990s says former President Alberto Fujimori never gave orders to violate human rights.

Santiago Martin Rivas also denied the existence of the death squad of which he has been convicted of membership.

His testimony at Mr Fujimori's trial in Lima completely contradicts previous interviews he gave to a journalist.

Peru's former leader is accused of corruption and human rights abuses between 1990 and 2000.

THE FUJIMORI ERA 1990: Wins a surprise victory at polls 1992: Dissolves Peru's congress with military backing, assuming greater control 1995: Restores congress and wins a second term 2000: Re-elected for third term amid vote-rigging claims 2000: Flees to Japan after Montesinos scandal breaks 2001-4: Japan refuses repeated attempts to extradite him 2005: Arrested on arrival in Chile on Peru's request 2007: Extradited to Peru

Giving testimony at the trial, Mr Martin Rivas said he had never received orders from Mr Fujimori to carry out massacres, and dismissed accusations that he had met him.

It was a dramatic about-face for the former army intelligence officer, who previously said that Mr Fujimori had known about and authorised the death squad killings for which he is on trial.

His evidence is also contradicted by several other members of the death squads who have given evidence in the trial and describe him as the leader and main instigator of the massacres they took part in.

Ex-President Fujimori is accused of authorising death squad killings

Mr Martin Rivas, a convicted member of the death squad which was known as La Colina, is serving a 20-year jail sentence for two massacres in the early 1990s, in which 25 people were killed.

Mr Fujimori is accused of authorising the killings, and could face 30 years in prison if convicted.

However, the testimony of this key witness will be a blow to the prosecution lawyers.