The groups said two opposition members had been shot dead, hundreds rounded up and imprisoned, while dozens had disappeared less than three weeks ahead of the 15 May legislative elections.

Bereket Simon, Ethiopian information minister and spokesman for the ruling party, dismissed the allegations as "baseless". The Ethiopian People’s Revolutionary Democratic Front, he said, had provided a code of conduct to its 600,000 members to prevent abuses.

"This is an absolute lie and pure fabrication," Bereket told reporters on Thursday. "Our members would be prosecuted if found to have taken part in abuses. Any diversion from this code of conduct would make our members accountable."

"We believe that the ruling party is enjoying its finest years and has enhanced credibility across the board," he added. "So why do we need to take part in such unethical practices when we are going to win the election with a landslide?"

The five opposition groups, the Oromo Federalist Democratic Movement (OFDM), the United Ethiopian Democratic Forces (UEDF), the Coalition for Unity and Democracy, the Ethiopian Pan Africanist Party and the United Ethiopian Democratic Party-Medhin, said the attacks took place over the last month.

"As election day approaches, opposition parties are facing extreme difficulties such as random killings, imprisonment and disappearances," Mesfin Nemera, OFDM spokesman told reporters in the capital, Addis Ababa.

Government militia, Mesfin added, had opened fire at opposition rallies to disperse crowds, while candidates and voters had been forced to hand over voting cards.

Beyene Petros, vice-chairman of the UEDF, said the violence threatened the pledge of "free and fair" elections. He added, however, that opposition parties would not boycott polling.

"If the government wants to stop this they can," he said at a press conference that was also attended by diplomats and election observers.

Beyene also criticised the National Election Board (NEB), who are running the campaign. "We have been writing letters every day to the NEB but I don’t think they have the desire to intervene," he said.

The NEB said it was not aware of the allegations. "We are not aware of these allegations formally," Kemal Bedri, the NEB chairman, said. "But we will investigate allegations, and if we are satisfied these things have happened we will ask for steps to be taken against alleged perpetrators of these crimes."

More than 25 million of Ethiopia's 71 million people have registered to vote in the upcoming elections. Some 35 political parties will vie for seats in the 547-seat Council of People's Representatives, according to NEB.

Voters will also elect representatives in nine regional state parliaments that appoint members of the 112-seat Council of the Federation, the upper house. The governing party and affiliated parties hold 519 of the current 547 seats in the federal parliament.

Source: IRIN