Uganda opposition leader charged with treason - lawyer
Besigye has disputed President Yoweri Museveni's victory in February's election and has been under house arrest for much of the time since.
He was arrested in the capital Kampala on Wednesday after staging his own swearing-in ceremony and whisked to Moroto, a town in the remote Karamoja region of the country.
"We have been informed by police today that Besigye appeared in court in Moroto and was charged with treason," lawyer Erias Lukwago told AFP.
Lukwago said his client was denied legal representation when charged with treason, and was remanded in custody until his next court appearance due on 25 May.
"It's absurd because none of us was there to represent him," he said.
Treason is a capital offence in Uganda, but the death penalty has not been carried out for years. Besigye was previously charged with treason in 2005, but the case against him was eventually dropped
Police spokesperson Fred Enanga confirmed the latest case against Besigye, but was unable to provide any further details of the charges.
A long-standing opponent of Museveni, Besigye has been frequently jailed, placed under house arrest, accused of both treason and rape, tear-gassed, beaten and hospitalised over the years.
Museveni, 71, who has been in power for three decades, was declared winner of the February poll with 61% of the vote.
He has rejected claims his victory was won through cheating and fraud.
Museveni was sworn in for a fifth term in office on Thursday at an event attended by foreign heads of state and diplomats.
He used the occasion to criticise the International Criminal Court (ICC) sparking a walk-out by diplomats from the US and European Union.