The alleged abduction in Kenya comes on the back of a similar experience suffered by 36 members of Dr Kizza Besigye political house in Kisumu four months ago.
Opposition stalwart Kizza Besigye went missing in Kenya at the weekend, his wife Winnie Byanyima and top party officials have said.
But Ms Byanyima says Dr Besigye is being held in a military detention facility in Uganda.
She has asked the government to "release my husband Dr Kizza Besigye from where he is being held immediately".
Dr Besigye was kidnapped last Saturday from Kenyan capital Nairobi where he had gone to attend Kenyan Opposition politician Martha Karua's book launch.
"I am now reliably informed that he is in a military jail in Kampala," UNAIDS executive director Byanyima said.
"We his family and his lawyers demand to see him. He is not a soldier. Why is he being held in a military jail?"
The government has yet to respond on the matter and security was tight-lipped at the time of writing this article.
Mr Wafula Oguttu, one of the top leaders at Dr Besigye's Katonga Road-based private office turn political base, said their leader had been abducted.
"It happened on Saturday evening at Riverside Nairobi," Mr Oguttu told the Nile Post.
"We have not yet established who picked him. It is abduction. Now four days!"
The mystery of Dr Besigye's disappearance in Nairobi comes on the back of FDC Katonga members being arrested in Kisumu four months ago and clandestinely handed over to the government back home.
The group of 36 have only recently been granted bail after they were charged with treason-related offences.
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The alleged abduction of Dr Besigye casts a spotlight on how the Ugandan government is treating the Opposition group that it repeatedly says it has crushed and defeated.
But it is also a damning indictment on the government of William Ruto that allows the same group into its territory only to illegally arrest them.
Both the Kenyan and Ugandan governments have yet to comment on the revelations concerning Besigye's whereabouts.
In the 1970s and 80s when Uganda faced political instability, Kenya provided a safe haven for thousands of exiles.
Some, like President Museveni, used the neighbouring country as a base to plan and launch a protracted guerilla war on the government of the time.
But 40 years appears to be too long a time in the past and the Kenya of today is no longer a place where Ugandan opposition can walk in and sip chai or eat sukuma wiki in peace.
