Police fired tear gas and rubber bullets Tuesday to disperse a crowd supporting Uganda's top opposition leader, who was detained while trying to walk to work. About a dozen supporters were charged with treason, a political aide said.
The police said opposition forces were trying to overthrow the government, the reason for the serious charge.
Opposition parties held "Walk to Work" protests in Uganda in April and May over high prices and political corruption. Those demonstrations sparked violence and standoffs with police. Nine people were killed.
Opposition supporters renewed the protests Monday, when demonstrators using rocks and police wielding tear gas clashed.
On Tuesday, Uganda's top opposition leader, Kizza Besigye, tried to walk from his countryside home outside the capital Kampala, but was detained by police, who took him back home. Besigye held an impromptu news conference, telling journalists that Uganda's constitution gives him the right to express himself by demonstrating.
Besigye tried to resume his walk but was again detained.
A political aide in Besigye's political party, Anne Mugisha, said that police arrested 13 people and originally charged them with inciting violence but later changed the charge to treason. Mugisha said it wasn't immediately clear if the 13 would be arraigned in court on that charge.
Uganda's police chief, Kale Kayihura, said that the opposition forces, collectively called Activists For Change, want to overthrow the government. He played an audio tape from an opposition meeting that he said demonstrated opposition plans to undermine the government.
"Its real objective is to plunge the country into chaos and in the process overthrow the government," Kayihura said, adding later: "This is a criminal offense called treason."
Kayihura said 45 people had been arrested in the most recent demonstrations.
Meanwhile, the police surrounded Besigye's home, while protesters laced nearby streets with large rocks, a tactic seen across the country during the April and May protests.
Police spokeswoman Judith Nabakooba said that police would not allow opposition supporters to disrupt peace around the country.
The price of food and gasoline have been rising in Uganda, squeezing the residents. President Yoweri Museveni has been in power 25 years, and Besigye and others accuse his regime of incompetence and corruption.
Last week three top government officials stepped down from their jobs while facing corruption charges. The three included Foreign Affairs Minister Sam Kutesa, ruling party chief whip John Nasasira and Mwesigwa Rukutana from the Labor Ministry stepped. The three pleaded innocent to charges of abuse of office and causing a financial loss. Kutesa is also accused of taking bribes from a company exploring for oil in the East African nation.