“In a row with a certain individual, the individual killed him,” Mr. Bereket said. “What they are trying to do is search for casualties and label them Arena. They are not into constructive engagement.”

A different opposition parliamentary candidate was beaten in Tigray on Sunday by members of the Ethiopian Army, and he was hospitalized, said Negasso Gidada, a former president of Ethiopia who has now joined the opposition. Like the man who was killed, the beating victim, Ayalew Beyene, had previously been arrested for attending opposition meetings or distributing campaign literature, he added.

“It is very bad news,” Mr. Negasso said. “My fear is such incidents may be intensifying.”

Government security forces killed at least 193 demonstrators during unrest after the country’s 2005 federal elections, which the opposition said were rigged. Birtukan Mideksa, widely considered to be the country’s most charismatic opposition figure, remains in prison, serving a life sentence issued in the aftermath of the disputed elections. Both the ruling party and the opposition have accused each other of seeking to foment violence around this year’s vote.

In local elections in 2008, opposition parties won just 3 of 3.6 million seats — virtually none of the huge number of local and by-election seats being contested — after two of the major groups boycotted the elections, citing intimidation and harassment, according to the State Department’s human rights report on Ethiopia.

Mr. Bereket, the government minister, who is also a senior official in Prime Minister Meles Zenawi’s Ethiopian People’s Revolutionary Democratic Front, said that the candidate beaten on Sunday had been pressuring a student who was not aligned with the ruling party to read opposition campaign literature and that the two had fought as a result.