Zimbabwe's opposition party on Friday challenged results that say its leader, Morgan Tsvangirai, has won the first round of the presidential election with 47.9 percent of the vote -- but not enough to avoid a runoff against President Robert Mugabe.

Zimbabwe President Robert Mugabe and opposition presidential candidate Morgan Tsvangirai will meet with leaders of southern African nations this weekend in an emergency summit to discuss the deepening political standoff in the country.

President Robert Mugabe faced an uncertain future for the first time in his 28-year rule of Zimbabwe, after the opposition claimed victory in last weekend's presidential race and his ruling party lost control of parliament, official results show.