Armed Zimbabwe riot police raided the headquarters of the opposition party embroiled in an election standoff with President Robert Mugabe Friday, forcing hundreds of people into the streets, news agencies report.

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.

Zimbabwe's ruling party ZANU-PF announced Friday it would back President Robert Mugabe in a runoff vote against opposition presidential candidate Morgan Tsvangirai, while the opposition party demanded an official tally from the first vote.

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.