Uganda's former intelligence chief, an outspoken critic of President Yoweri Museveni, was charged in a military court Tuesday for taking part in politics against army law, his lawyer said.

General David Sejusa, 61, denied all five charges, which also included being absent without leave.

Sejusa, who was arrested by soldiers at his home on Sunday morning, appeared at the court martial in Kampala, dressed in a white shirt. He was remanded in custody until February 9 ahead of a bail hearing.

Sejusa said the charges were "ridiculous", his lawyer Ladislaus Rwakafuuzi told AFP.

Tensions are mounting in the east African nation ahead of a February 18 presidential poll.

"It is a political move, because he's supporting the opposition and these people want to get him out of circulation," Rwakafuuzi added.

Seven opposition candidates are vying to end Museveni's 30-year rule, and there are fears violence could mar the campaign, with all sides accusing each other of arming militias to press their claims to power.

Sejusa was once one of Uganda's top military bosses, serving as intelligence chief and as a close advisor to Museveni, who has been in power since 1986. He went into exile in 2013 to Britain after a confidential memo he wrote was leaked to the press, causing a political storm.

The memo claimed Museveni was grooming his son, special forces commander Muhoozi Kainerugaba, to succeed him and that those in the army opposed to the supposed succession plan risked being assassinated. While in exile, he set up an opposition political party, returning in 2015.

Government spokesman Ofwono Opondo on Monday issued fresh warnings that opposition parties were organizing militia gangs, including plots to erect road blocks on main roads to "paralyse economic activities" and to "attack several offices of the Electoral Commission."

Opondo said police were investigating claims Sejusa was linked to some of these groups.

"Under the guise of mobilising their supporters for vote protection on polling day, the same opposition elements have sinister plans to eventually turn into acts of civil disobedience," Opondo said.

Opposition parties have rejected previous allegations they are organizing militia forces.