Zimbabwe's Constitutional Court said it will rule on Friday after hearing the main opposition party's challenge to the results of last month's presidential election, the first without longtime leader Robert Mugabe on the ballot.

Police barricaded streets in the capital, Harare, on Wednesday amid high tensions over the case which will decide if the victory of President Emmerson Mnangagwa, a former Mugabe enforcer, is valid. The opposition claims "gross mathematical errors" and seeks a fresh election or a declaration that its candidate, 40-year-old Nelson Chamisa, won.

The Zimbabwe Electoral Commission declared Mnangagwa narrowly won with 50.8 percent of the vote, avoiding a runoff. It said Chamisa received 44.3 percent.

Many hoped the peaceful vote on July 30 would launch a new era for Zimbabwe after Mugabe stepped down in November under military pressure, but two days later six people were killed when troops swept into the capital to disperse opposition protesters.

Western election observers and diplomats condemned the "excessive" use of force. European Union election observers were in court on Wednesday; the 75-year-old Mnangagwa badly needs a credible electoral process as a key step in removing international sanctions.

The opposition claims the electoral commission bumped up Mnangagwa's figures through double counts and the creation of "ghost" polling stations. It also alleges that some polling stations recorded more voters than those registered.