GUATEMALA CITY, March 3 (Reuters) - The family of Guatemala's defense minister received death threats after the government promised to open long-sealed military archives that could reveal army abuses during the country's civil war, President Alvaro Colom said on Tuesday.

Colom vowed last year to open the archives to allow investigators to scour them for evidence of army-backed massacres during the 1960-1996 conflict between the government and leftist guerrillas.

"We have information that the defense minister's family members received death threats from a group of ex-army officials upset about the de-classification of potentially compromising archives," Colom said at a news conference.

Almost a quarter of a million people were killed or disappeared during the war, with the bulk of the victims Mayan civilians, and a United Nations-backed truth commission found 85 percent of the murders were committed by the army.

Despite the threats, Defense Minister Abraham Valenzuela still intends to make public thousands of army documents from as far back as the 1954 U.S.-supported military coup against the social democratic government of Jacobo Arbenz, said Colom.

"We are no longer at war, there is nothing to hide," said Colom, who was elected in 2007 on a leftist platform of reconciliation and poverty reduction.

The president's uncle -- also a leftist politician who ran for president -- was killed in an army ambush in 1979.

No date has been given for the opening of the archives and human rights organizations have accused Colom of foot-dragging.

On Tuesday, Colom announced the creation of a special panel to review the files and determine which must remain secret for national security reasons.

A previous defense minister was replaced after he refused to follow the president's order to open the archives, stating publicly Colom was overstepping his mandate. (Reporting by Herbert Hernandez; writing by Mica Rosenberg; editing by Mohammad Zargham)

AlertNet news is provided by