The National Unity Platform president, Robert Kyagulanyi, is to undergo surgery.
This follows the incident at Bulindo, Kira Municipality, were he was shot at by the Police.
NUP spokesperson Joel Ssenyonyi in a press briefing said "Kyagulanyi is to get surgery to remove the teargas canister fragments from his leg."
The Opposition is recieving emergency treatment from the St Francis Hospital Nsambya.
"He is in pain but has been sedated," says Ssenyonyi.
Police on Tuesday refuted claims that Mr Kyagulanyi was shot, instead suggesting he had "stumbled and got injured while getting into his car".
Mr Kyagulanyi, 42, is a former pop star who turned to politics, first taking the Kyaddondo East seat in a by-election in 2017.
In 2021, he challenged President Museveni in the presidential election after taking over the mantle from Dr Kizza Besigye who had unsuccessfully stood for the top executive seat four times.
Museveni secured 5.85 million votes, or 58.64 percent, of the total votes cast, while Bobi Wine won 3.48 million votes or 34.83 percent, according to official figures.
Mr Kyagulanyi disputed the results, saying the elections were flawed.
But with his party securing the majority number of legislators to the Eleventh Parliament, he became the Opposition leader.