HARARE (AFP) - Zimbabwe, already facing a presidential run-off, hit new electoral turmoil on Wednesday after the ruling party and Opposition filed legal challenges to half of the parliamentary results from March's polls. State media said President Robert Mugabe's ZANU-PF party, which lost its majority for the first time in the March 29 election, was now contesting the outcome in 53 of the 210 constituencies while the Opposition was disputing 52. Meanwhile, the African Union urged all sides to shun violence in the build-up to the presidential election run-off as the opposition claimed 25 of its supporters had now been killed since the original polling day. The Herald newspaper, the government's mouthpiece, said the volume of petitions filed with the electoral court had prompted the country's Chief Justice to appoint 17 more judges there. Given that the electoral court can take up to six months to rule on the petitions, the latest development is likely to increase a power vacuum at a time when the outcome of the presidential contest is still up in the air. Master of the High Court Charles Nyatanga, effectively the chief legal administrator, was quoted as saying his office had "received 105 petitions, which have to be determined within six months in terms of the Electoral Act." The legislative election saw ZANU-PF lose its majority in parliament for the first time since the former British colony's independence 28 years ago, with the MDC taking 109 seats against 97 for Mugabe's party. Opposition leader Morgan Tsvangirai also beat Mugabe in simultaneous presidential elections but fell short of an overall majority needed to avoid a second round. According to the MDC, the five latest victims were beaten to death by suspected ZANU-PF supporters during a Monday night raid on several villages in a farming area north of the capital. "We think the actual (overall) death toll is even higher because there are some farming areas that have been cordoned off by militias and vigilante groups," party spokesman Nelson Chamisa told AFP. The African Union urged all sides to shun violence in the countdown to the run-off, as British Prime Minister Gordon Brown noted the key role to be played by the organisation and the Southern African Development Community. "I think it's important that ... the African Union and SADC and all those who have an interest in the future of Zimbabwe put pressure, so that any elections that take place in Zimbabwe are free and fair," he said. An AU statement issued at its Addis Ababa headquarters urged "all the Zimbabwe political actors to conduct their activities in a free, transparent, tolerant, and non-violent manner to enable eligible Zimbabweans to exercise their democratic rights."