Ethiopia's main opposition parties on Tuesday won the first round battle in their attempts to challenge the ruling Ethiopian People's Revolutionary Democratic Front's (EPRDF) landslide victory in last month's general elections. "At least we have managed to have our case filed at the court," Gidada Negasso, Ethiopia's former president, told PANA on phone after the Supreme Court allowed the opposition coalition to challenge the EPRDF landslide win in the 23 May elections.