Dozens of campaign staff working for Bobi Wine, Uganda's leading opposition candidate in next week's presidential election, are being held in a military barracks after authorities defied court orders to release them, Wine's lawyer said on Friday.

Singer-turned-lawmaker Wine, 38, whose real name is Robert Kyagulanyi, has been arrested multiple times while campaigning ahead of the January 14 vote for breaking laws governing public order and Covid-19 restrictions on large gatherings.

Wine is considered to be the leading challenger to President Yoweri Museveni, who has been in office since 1986.

On December 30, 118 Wine supporters and staff were arrested in the town of Kalangala on Bugala Island in Lake Victoria, where they had travelled to campaign, Wine's lawyer George Musisi told Reuters.

A court in Masaka, about 120 km (75 miles) southwest of the capital Kampala, ordered their release on Monday but Uganda's prisons service refused to comply, Musisi told Reuters.

After obtaining more court release documents on Thursday, 46 people, mostly supporters, were freed while 72, mainly campaign staff, were taken to Makindye military barracks on the outskirts of Kampala, he said.

Military spokesperson Flavia Byekwaso told Reuters she needed time to study the situation before responding.

Prisons service spokesperson Frank Baine did not answer a phone call to request comment.

Wine's lawyer said they were preparing another court application for their release. He said the people freed on Thursday said they had been tortured.

Human Rights Watch, a watchdog based in New York, said in November that Museveni's government was using coronavirus restrictions as a pretext to violate rights and crack down on the opposition and the media.

Wine's rallies are usually broken up by the security forces. In November, 54 people were killed as security forces battled to quell protests after Wine had been detained.