The body of a prominent Argentine businessman was discovered last night, a week after his family reported him missing. The victim, Marcelo Dupont, 46, was the brother of a diplomat who recently has charged the military government with involvement in a notorious case resulting in the death of another envoy four years ago.

The murder of Dupont, a well-known advertising executive, sent shock waves through this capital today.

"It looks like psychological terrorism by autonomous right-wing groups in the government," said a Western diplomat. "It appears to be part of a campaign of intimidation -- it could happen to anybody."

Police reports said Dupont had been asphyxiated and his body flung from a four-story building under construction not far from the city center. Police said he was the object of an intense search by law enforcement officers.

Dupont was the older brother of Gregorio Dupont, an ex-Foreign Ministry official and one of a number of former government workers who recently have linked past cases of disappearances and murder to the military government.

Gregorio Dupont charged last month that Elena Holmberg -- an Argentine diplomat murdered in 1978 -- told him days before she disappeared that she knew of a financial deal between Argentina's leftist Montonero terrorists and Adm. Emilio Massera, then a member of the ruling junta. Massera has denied the charge and filed a slander suit against the younger Dupont.

Gregorio Dupont identified the body of his brother this morning. Marcelo Dupont reportedly told friends before his disappearance that he was being followed by a vehicle of the type favored by security forces during massive "disappearances" of leftist guerrillas in the 1970s.

Carlos Contin, President of the Radical Civil Union, one of the country's largest political groupings, said the Dupont case shows "that in the last analysis these military regimes don't even know how to maintain order."

The murder is viewed here by some observers as a major blow to the rule of President Reynaldo Bignone, who has sought to rein in human-rights abuses as his government enters into discussions with political groups over the return to democratic government, scheduled for 1984.

Rights sources say that 14 other people had "disappeared" this year. One, Anna Maria Fernandez, was found dead Feb. 12. The others eventually were released.