Police have found the bodies of three Salvadorean politicians and their driver in a bullet-riddled and burnt-out car outside Guatemala City
The three men were members of the governing Arena party of El Salvador, and were deputies to the Central American Parliament.
One of them was the son of the party's late founder, Roberto D'Aubuisson.
D'Aubuisson was accused of being behind the assassination of Archbishop Oscar Arnulfo Romero in 1980.
The four killings followed a controversial request by the Salvadorean Congress to honour Roberto D'Aubuisson, who died of cancer in 1990.
The Salvadorean victims have been named as Eduardo D'Aubuisson, William Pichinte and Jose Ramon Gonzalez.
Their driver has not been named.
Police had launched a search for the four men late on Monday afternoon after they received a report that they had not yet arrived at their hotel.
The Central American Parliament has 132 members representing five of the seven central American nations.
It was set up in 1986 to aid political integration in central America, but it does not replace local legislatures.
Salvadoran president condemns killings of 3 legislators in Guatemala