Uganda's main opposition leader Bobi Wine, who has emerged as the most formidable opponent of veteran President Yoweri Museveni, was shot in the leg by security agents in a northern suburb of the capital Kampala on Tuesday, his party said.

Wine, a pop star turned politician whose real name is Robert Kyagulanyi, finished runner-up in the 2021 presidential election behind Museveni, who has ruled the East African country for nearly four decades.

Wine's party, the National Unity Platform, said in a post on the X platform that "Security operatives have made an attempt (on his life)". "He was shot in the leg and seriously injured."

The police said officers had attempted to block Wine and his team from marching down a road, resulting in an altercation where Wine sustained injuries. An investigation would be conducted to clarify the facts, the police said in a statement on X.

"Police officers on site claim he stumbled while getting into his vehicle, causing the injury, whereas Hon. Kyagulanyi and his team assert that he was shot," the police said.

A video shared widely on social media showed NUP party officials helping Wine hobble out of the Najeem Medical Centre in the Bulindo neighbourhood. Wine appeared to have a bleeding wound on the shin of his left leg and was grimacing in pain.

"We condemn this cowardly action; yet another attempt on his life. The continuing violence meted out on those opposed to the Museveni regime must be condemned by all people of good conscience," NUP party Secretary General David Lewis Rubongoya wrote on the social media platform X.

Museveni's government has been accused by opponents and human rights activists of stifling the opposition, something Museveni denies.

A U.S. State Department spokesperson told reporters on Tuesday that Washington was "concerned that violence against opposition voices means the democratic space continues to shrink in Uganda."

Wine has amassed huge support amongst the youth in Uganda, a nation of 46 million, with many wooed initially by his rags-to-riches story as a pop star from the ghetto, and in recent years by his bold attacks on Museveni's government.