Kampala - Retired army colonel and medical doctor Kizze Besigye confirmed on Saturday that he knew about an affair which Ugandan President Yoweri Museveni once had with his wife, but said that this had not been the cause of the two men's political rivalry.

Besigye, who was runner-up to Museveni in the presidential elections in February 2006, confirmed to Deutsche Presse-Agentur dpa that the president had had an affair with his wife Winnie Byanyima.

But Besigye insisted that the differences with his former ally was over politics.

"Yes, they had a relationship but I do not consider that this (Museveni-Winnie) relationship has a connection with his relationship with me," the physician told dpa by telephone.

"What Museveni does to me, he can do it to anybody else who opposes him."

Earlier, the independent newspaper The Daily Monitor had quoted the 49-year-old politician as telling a local radio station that there was no doubt "Winnie had a relationship with president Museveni but my differences with Museveni were long before this (Besigye- Winnie) relationship was there."

Besigye told dpa that "Museveni can act with viciousness if anyone goes against him. It is all to do with power."

Besigye was a senior army and government official in Museveni's government before he fell out with his former boss in the late 1990s after publicly calling for reforms in the ruling party to curb corruption and to open the country up to multi-party politics.

He vied for the presidency twice, in 2001 and in the latest elections after returning from exile in South Africa in late 2005.

Soon after returning from exile, Besigye was arrested and slapped with a variety of charges including rape, cases which are widely believed to have been politically-motivated. A court cleared

him of the rape charge but he still stands trial for treason.

Local reports say people believe the battles between the two men stem from their rivalry over Winnie, a professional engineer-turned politician and women's rights advocate who now works at the headquarters of the African Union in Ethiopia.

The reports said Museveni's affair with Winnie came during the 1981-86 guerrilla war that propelled him into power. Besigye was his personal doctor during the insurgency.

Before Besigye's first comment on his wife's relationship with the head of state in a story run in The Daily Monitor, all three major political parties kept silent on the subject during the

election campaigning ahead of the elections last February 23.

But a spokesperson for Besigye's Forum for Democratic Party did not mince words when reached by dpa Saturday. Party spokesperson Wafula

Oguttu said Museveni still loved Winnie and might not give up on her.

"Museveni still loves Winnie. He has never given up on her up to this day. I think Museveni has a negative attitude against Besigye because of Winnie.

"We also think that Museveni saw Besigye as a man who disrespected him when he went against him in politics," Oguttu said, claiming that Museveni had kept a number of mistresses, but "it was only Winnie who was courageous enough" to leave him. - Sapa-dpa