The health of detained veteran Ugandan opposition figure Kizza Besigye has "reached a critical and deteriorating state," his party says, after he was taken overnight to a medical facility in the capital, Kampala.

The 69-year-old politician was driven to a private medical facility under "heavy security," the People's Front for Freedom (PFF) party said, without specifying what he is suffering from.

However, prison authorities denied that Besigye's health was dire, describing his overnight visit to a doctor as a "general check-up".

Besigye, a former personal doctor to President Yoweri Museveni and one of his longest-standing political rivals, has been in detention since November 2024.

The PFF leader was charged in a military court with treason, which carries the death sentence, as well as illegal possession of a firearm and threatening national security. He denies the accusations.