ACCRA (Reuters) - Ghana's Supreme Court said on Wednesday it will rule by August 29 on an opposition challenge to the result of December's presidential election that was won by incumbent John Mahama.

Justice William Atuguba, presiding over the closing arguments in the high profile and protracted election dispute, told a packed court that he would issue the verdict 15 days after a further hearing due on August 14.

Opposition leader Nana Akufo-Addo has challenged the outcome of the 2012 poll. He claims that the ruling NDC party tampered with results to boost Mahama's share of the vote to 50.7 percent, handing him a first-round victory.

The counsel for the opposition argued that the tallies of votes cast contained enough irregularities to sway the election result in favour of Akufo-Addo.

"These malpractices and irregularities have a material effect on the result," said Philip Addison, a lawyer for the opposition NPP party.

Mahama's lawyers said no evidence of fraud was presented during the proceedings and any technical problems should not be used to invalidate citizens' right to vote.

(Reporting by Matthew Mpoke Bigg and Kwasi Kpodo; Editing by David Lewis and David Evans)