RIO DE JANEIRO -- Lino Oviedo, a candidate in Paraguay's presidential elections and one of the country's most polarizing political figures, was killed in a helicopter crash Saturday night while returning from a political rally in northern Paraguay, government officials said Sunday.
The fiery crash -- which killed Mr. Oviedo, 69, an aide and the pilot of the helicopter -- opens a new phase of uncertainty in Paraguay, one of Latin America's most politically unstable countries. After authorities confirmed his death and called it an accident, officials in his party, the National Union of Ethical Citizens, immediately questioned whether Mr. Oviedo had been assassinated.
The death of Mr. Oviedo, a retired general who had led Paraguay's army, brought an end to a tumultuous political career.
He initially gained prominence in 1989, when he helped topple Gen. Alfredo Stroessner, the dictator who ruled Paraguay for 35 years.
Mr. Oviedo fled the country, seeking exile first in Argentina, then in Brazil, after being charged with organizing a coup attempt in 1996 against Juan Carlos Wasmosy, then Paraguay's president.
The authorities also indicted Mr. Oviedo on charges of masterminding the assassination of Luis Maria Argana, the vice president who was killed by gunmen outside Asuncion in March 1999. But after Mr. Oviedo returned to Paraguay in 2004 and served time in prison on the coup-plotting conviction, Paraguay's Supreme Court absolved him of the various charges.
He took up a hard-charging political career, campaigning as a populist who nimbly used Guarani, Paraguay's widely spoken indigenous language, in his speeches. He came in third in the country's last presidential vote, in 2008.
Paraguay was officially commemorating Stroessner's overthrow Sunday, making the timing of the helicopter crash questionable for some of Mr. Oviedo's political supporters.
"This is a message from" shadowy organizations, Cesar Durand, a spokesman for Mr. Oviedo's party, told Radio Nanduti.
The election comes after a stretch of political turmoil in Paraguay in which Paraguay's Senate hastily ousted the president, Fernando Lugo, from office in June.
If Horacio Cartes, a banking and tobacco magnate, 56, holds his lead, the presidency will return to the Colorado Party, which long dominated Paraguay. Still, his campaign is facing questions over his business dealings. State Department diplomatic cables obtained by WikiLeaks revealed claims in 2007 that a bank under Mr. Cartes' control was involved in a great deal of Paraguay's money-laundering activities.
Mr. Cartes has rejected the claims, calling them "rubbish."