Kampala, Uganda ? President Yoweri Museveni was declared the winner Saturday in Uganda’s first multiparty election in 25 years, but the opposition claimed its own tally had the incumbent trailing in a ballot that observers say was marred by government abuses.

Museveni supporters celebrated in the streets, while police fired tear gas and bullets to chase off a stone-throwing crowd outside opposition headquarters. Military police split into small groups and walked through nearby neighborhoods after the crowd scattered.

Assuman Mugenyi, the police spokesman, said militant elements in the opposition party planned to stage a riot and authorities were forced to disperse them.

Museveni, 62, was once hailed as a reformer in this central African country that suffered under the brutal dictator Idi Amin in the 1970s. He agreed to term limits and instituted economic liberalization.

But he has upset the United States and other nations by intervening in Congo’s civil war, boosting military spending and reneging on a 2001 promise to retire from politics. The West has cut aid to the government in reaction to his moves to consolidate power and quash dissent.

In power since 1986, Museveni lifted a presidential two-term limit so he could run again.