The highest court in El Salvador has ordered President Salvador Sánchez Cerén to testify in the case of a South African ambassador to the country who was kidnapped and later killed.

Archibald Gardner Dunn was seized by armed men outside the embassy on 28 November 1979.

Almost a year later, the left-wing rebel group Popular Liberation Forces said it had killed the diplomat.

President Sánchez Cerén was the group's second in command at the time.

In presidential elections held in March 2014, he became the first former rebel to lead El Salvador.

President Sánchez Cerén has not yet commented on the court's ruling ordering him to give evidence over Dunn's disappearance.