The BBC's Lindsey Marnoch: "A potentially explosive memorandum"

Newly declassified documents throw new light on the death of Charles Horman, whose death inspired the Hollywood film Missing, starring Jack Lemmon.

Horman, a left-wing activist and freelance reporter working in Chile, was murdered shortly after the military coup that brought dictator Augusto Pinochet to power.

The release of the documents by the US State Department came as a British magistrate ruled that General Pinochet can be extradited to Spain to face charges of torture and human rights abuses.

Jack Lemmon, star of Missing, which raised the plight of Horman's family

The Horman document, which is dated 1976, reads: "US intelligence may have played an unfortunate part in Horman's death.

"At best, (the CIA role) was limited to providing or confirming information that helped motivate his murder by the GOC (Government of Chile)," the report added, citing circumstantial evidence.

BBC's James Reynolds: "The documents will be inspected closely here in Chile"

"At worst, US intelligence was aware the GOC saw Horman in a rather serious light and US officials did nothing to discourage the logical outcome of the GOC paranoia."

It goes on: "This case remains bothersome. The connotations for the Executive (branch) are not good.

Salvador Allende: The US was nervous about his Marxist rule

"In the Hill (Capitol Hill), academic community, the press and the Horman family, the intimations are of negligence on our part, or worse, complicity in Horman's death."

Horman was killed in the chaotic aftermath of the bloody coup against the democratically-elected leader Salvador Allende.

US officials considered Allende's Marxist regime to be unsettling for US interests in South America.

The 29-year-old American journalist was taken from his home and rounded up with other suspected leftists at a football stadium in the Chilean capital, Santiago. He was later murdered and his family spent considerable effort tracking down his body.

The 1982 film Missing generated widespread controversy by alleging the US government had been involved in his murder.

Files handed to widow

At the time it drew vigorous objections from State Department officials, including Nathaniel Davis, then the US ambassador to Chile.

The newly released two-page document was handed to Mr Horman's widow, Joyce, by the National Security Archive, a research group at George Washington University.

It is part of a wider release of more than 1,000 classified US government files relating to events leading up to and following the coup in Chile.

They include files held by the State Department, the CIA, the National Archives, the FBI and the Defense Department.

This is the second set of documents relating to Chile's years of military rule to be released by the US government. The first batch was released in June and a final set is still to come.

The Clinton administration has been keen to stress that the release of the files has nothing to do with the legal proceedings currently facing Gen Pinochet.