Judge Jorge Guzman Urquilla on Saturday accepted the request to reopen the probe filed by human rights advocate Ovidio Mauricio's organization and two other groups, according to the The Associated Press agency.

The decision was based on a July ruling by the country's Supreme Court that overturned a law granting amnesty for war crimes during El Salvador's 1979-1992 civil war, in which at least 75,000 people were killed.

A UN truth commission found that the army had massacred at least 500 people in El Mozote over three days in December 1981. Victims' rights advocates put the number closer to 1,000. Its report put responsibility for the massacre on Colonel Domingo Monterrosa, commander of the Atlacatl battalion, operations chief  Colonel Armando Azmitia and six other officers. Monterrosa and Azmitia died when a bomb went off in their helicopter in 1984.

El Mozote villagers were reportedly mainly evangelical Christians who had tried to remain neutral in the conflict and therefore decided not to flee when rebel sympathizers nearby ran away from an army advance.

Many of the bodies were dumped in the interior of a small church and burned. David Morales, a former government human rights prosecutor, said that in one grave alone forensic experts found "136 skeletons of girls and boys, with an average age of 6 years."

Touchy subject

The ruling has upset both former military men and the current government, which grew out of the rebel Farabundo Marti National Liberation Front. The army - and the US government that trained the Atlacatl battalion involved in the killings - initially denied any massacre had taken place.

The Inter-American Court of Human Rights has ruled that El Salvador should pay reparations to the victims, a decision the government accepted in 2012 as it apologized for the massacre.

jbh/cmk (AP, Reuters)