Zimbabwean police on Sunday arrested an aide to Morgan Tsvangirai, President Robert Mugabe's main rival in upcoming polls, after he reported an irregularity in early voting.
The Movement for Democratic Change said Morgan Komichi was arrested after informing the electoral commission that ballot papers marked for Tsvangirai had been found in a dustbin after security forces voted at the Harare International Conference Centre two weeks ahead of nationwide polling on July 31.
"Around 6:00 am (0400 GMT) our deputy national chairman, Honourable Morgan Komichi, who is a deputy minister of transport, was picked up at his home by the police," the MDC's Nelson Chamisa told reporters.
Police spokeswoman Charity Charamba confirmed the arrest just three days before general elections that will end an uneasy unity government between Mugabe, 89, and his archrival Prime Minister Morgan Tsvangirai.
"Yes, he has been arrested," she told AFP.
Komichi, Tsvangirai's delegate at the Zimbabwe Electoral Commission (ZEC), this week handed the polling panel an envelope with ballot papers in favour of Tsvangirai.
The MDC said several such ballots had been dumped in a dustbin at the conference centre where security forces, who will be on duty in Wednesday's polls, voted early on July 14 and 15.
Charamba later told a news conference that police will charge Komichi for contravening electoral laws if he refuses to disclose who brought the alleged irregularity to his attention.
"As long as he refuses to disclose the identity of this person the police will hold him accountable, therefore he becomes the prime suspect," she said.
"This is a very urgent and serious matter that will have bearing on the election process and therefore cannot be left for any other time except now."
The MDC's Chamisa earlier on Sunday accused the ZEC of going on a witch hunt instead of dealing with the dumped ballot issue.
"There is no denial of the fact that indeed it's an authentic ballot paper and indeed the ballot paper was found in the dustbin, but of course they want to know the whistle-blower," Chamisa said.
"We believe that ZEC and not Komichi have a lot of questions to answer," he added.
"If there is any investigation, the theatre of investigations is supposed to be ZEC."
Chamisa reiterated Tsvangirai's fears of a rigged election when voters on Wednesday pick a president and a parliament.
"The development we have witnessed seriously demonstrates a dent on the credibility of this election," he said, questioning the electoral commission's neutrality.
Chamisa complained that the MDC, which won more votes than Mugabe's Zanu-PF in the 2008 parliamentary polls, has been denied important election-related information.
"The voters' roll has not been availed to us, we don't know who is printing the ballot papers," he said.
Violence erupted after the first round of the 2008 polls didn't deliver a conclusive winner.
Mugabe and Tsvangirai were forced to form a power-sharing government a year later.