Soldiers and police surrounded the High Court in Kampala and refused entry to diplomats and journalists, allowing in only Dr Besigye's wife and a few senior officials from his political party.
"For security reasons, we are not allowing anybody to go in," regional
police commander Oyoo Nyeko told a group seeking entry.
"Just stand outside, we shall let you know when to enter. This is for your own security."
Strike protest
The security forces were deployed around the court just a day after Ugandan lawyers staged a one-day strike.
The strike was to protest military interference in Dr Bisigye's case, which they said violated judicial independence and rule of law.
Inside, Dr Besigye completed formalities for his provisional release on bail ordered last week by Judge James Ogoola.
But he was expected to remain in prison because of separate charges against him by a military court, his lawyer said.
"As far as we are concerned, Besigye has signed his bail papers and he is a
free man now," attorney Yusuf Nsibambi said.
"But the prison says it has received a remand warrant ... to continue his detention pending the charges against him before the military court.”
"We are going to challenge the warrant because the military court is
subordinate to the High Court," Mr Nsibambi added.
Rape charges
Dr Besigye, the leader of the opposition Forum for Democratic Change (FDC) who is seen as the top rival to Ugandan President Yoweri Museveni in March
elections, faces treason and rape charges in the High Court.
However he and 22 co-defendants also face terrorism and illegal weapons
possession charges before a military tribunal.
Dr Besigye and his supporters maintain the charges stem from government accusations he tried to overthrow the government.
They say the accusations are politically motivated and aimed at preventing Dr Besigye from challenging President Museveni in the upcoming polls, something the president has vehemently denied.
If convicted on the treason and terrorism counts, the FDC leader could face the death penalty.
Dr Besigye returned to the east African country after four years of self-imposed exile on October 26, vowing to fight President Museveni's "dictatorship" in the upcoming polls.
He was detained three weeks later on allegations he conspired with rebel
groups to oust President Museveni in a coup, sparking deadly riots in the capital where authorities have now banned rallies in his support.