Yoweri Museveni UK Somalia Conference
President Yoweri Museveni of Uganda meets Prime Minister Theresa May during the London Conference on Somalia at Lancaster House on May 11, 2017 in London, England. Hannah McKay - WPA Pool/Getty Images

Police shot dead two people Wednesday while seeking to foil a political rally in a remote part of Uganda, an opposition official said, amid rising tensions over attempts to extend the longtime president's rule.

A campaign event in the southwestern town of Rukungiri turned violent when police blocked hundreds of opposition supporters from entering a stadium, said Ingrid Turinawe, the mobilization secretary of the Forum for Democratic Change party.

"As soon as we arrived they started shooting," she said.

Police used tear gas and live ammunition to disperse the crowd, but people lingered and eventually forced the police to flee, she said.

A Ugandan police spokesman did not answer calls for comment.

Opposition leaders are trying to mobilize against efforts to remove an age barrier in the constitution that prevents 73-year-old President Yoweri Museveni from extending his rule when his current term expires in 2021.

The constitution bars anyone who is 75 or older from contesting the presidency.

The United States is urging Uganda's government to protect basic freedoms "without fear of intimidation," and Amnesty International says authorities "must end their absurd attempts to silence people opposed to scrapping the presidential age limit."

Museveni, a U.S. ally on regional security, took power by force in 1986 and was re-elected last year in a poll marred by allegations of fraud and voter intimidation.

Although Museveni warned in the past that Africa's problem was leaders "who want to overstay in power," he has since said he was speaking about leaders who were not elected.

Uganda's ruling party enjoys an overwhelming majority in the national assembly and the bill to remove the age barrier is expected to pass despite the spirited efforts of opposition leaders, who wear red bandanas as a sign of what they call their resistance to Museveni's long rule.

There are no term limits in Uganda's constitution, one of the reasons that critics see the age barrier as a measure against any attempts at a life presidency.

Uganda has not seen a peaceful transfer of power since independence from Britain in 1962.

Uganda Protest Yoweri Museveni
Uganda Protest Yoweri Museveni