The leading challenger to Ugandan President Yoweri Museveni said on Tuesday he had no confidence that elections this week would be free or fair and accused the police of increasing violence ahead of the vote.
Kizza Besigye, a long-time opposition leader who has lost three previous elections, told reporters the "overwhelming enthusiasm" for change after three decades of Museveni rule "has caused panic in the no-change camp".
"That is why, yesterday, elements of the Uganda police and other security agencies unleashed violence on our supporters and sabotaged our campaign in Kampala," he said. "The election has no chance of being free and fair."
Besigye spoke a day after police stormed his rally in the capital Kampala with tear gas, killing one person and injuring 19 others, and briefly held him in custody.
Police also said that Besigye's supporters had been on a "rampage", looting and damaging property.
It was the worst violence since the campaign opened three months ago and heightened tensions before the Feb. 18 vote.
Also on Monday, a government spokesman said all campaigning had been prohibited in Kampala's central business district, where Besigye's supporters had gathered.
The election is expected to be one of the toughest yet for Museveni, 71, a key ally of the West who came to power in 1986 after waging a five-year guerrilla war.
Ugandan political watchers say voters have grown impatient with high unemployment and the poor state of the country's schools and health centres, giving fresh life to Museveni's challengers.
The United States last week supported calls for a peaceful, transparent and credible vote.
Museveni, Besigye and a second major challenger, former prime minister Amama Mbabazi, were all staging final rallies on Tuesday, a national holiday.
Besigye, who has been repeatedly detained by police, has said he is a frequent target of government intimidation tactics and has accused Museveni of rigging polls and using state funds to prop up his own party, the National Resistance Movement.
He said he had no plans to change his campaign schedule after the violence on Monday.
"This is nothing new," he said. "We are in this to overwhelm the unfreeness and the unfairness ... We'll just continue fighting."
Officials say Besigye has simply been punished for engaging in illegal behaviour, such as breaking rules on where and when campaign activities were allowed.