HARARE, Zimbabwe?The government on Wednesday declared President Robert Mugabe the winner of the most bitter presidential election in Zimbabwe’s history, a vote observers said was deeply marred by ruling party violence.

Mugabe’s opponent, Morgan Tsvangirai, denounced the results as “the biggest election fraud I have ever witnessed in my life.” Tsvangirai, a former labor leader, had presented the first real electoral challenge to Mugabe since the president led Zimbabwe to independence 22 years ago.

Zimbabwean security forces were on “full alert” to quash any unrest as the results were announced early Wednesday morning, state television reported.

Military police set up roadblocks on main roads leading into the capital, Harare, and military helicopters flew over the city of Bulawayo, an opposition stronghold. Many businesses were closed Wednesday, fearing the possibility of violence.