Amnesty International has criticised Ugandan authorities for placing ever-tighter "illegitimate restrictions" on freedom of assembly and peaceful assembly.

The UK-based rights organisation, in a report on Monday, said that the authorities' lack of tolerance towards their critics is leading to repressive policies towards opposition politicians, along with restrictions on media and rights activists.

This came as Ugandan police released opposition leader Kizza Besigye, hours after detaining him for the second time in a month, but warned they would keep detaining him if he continued to take part in protests against surging prices.

Besigye was mobbed by supporters after he walked free from the Kasangati police station on the outskirts of the capital, Kampala, and drove off in his car, a witness said. A police spokesperson confirmed Besigye's release.

"The Ugandan authorities are creating a climate where it is becoming increasingly difficult for people to freely criticise government officials, their policies or practices," Godfrey Odongo, Amnesty International's Uganda researcher, said in a statement.

The government has banned public protest, is introducing further restrictive legislation on public meetings and media, and has threatened to scrap pre-trial bail for involvement in peaceful protest.

Serious threat

Opposition activists have sought in past weeks to revive street demonstrations against the surging rate of inflation in east Africa's third biggest economy after a wave of deadly protests in April and May were crushed by President Yoweri Museveni.

The protest movement, led by the Activists 4 Change (A4C) group, has struggled to rally large numbers since then, mainly because Besigye has largely stayed away from demonstrations or been prevented from participating.

Political analysts say the latest bout of civil action is unlikely to grow into a serious threat to the government given the international community's muted response to the previous crackdown.

But some backers of Besigye, defeated by Museveni at the ballot box for the third time in February, vowed not to cave in to government pressure.

"The police have shown they are determined to violate (Besigye's) rights and we are saying we will be with him every time he walks," said 29-year-old Martin Lutalo.

Uganda's police force said last week it would keep Besigye under house arrest until he promised to stop participating in the anti-government protests. A Ugandan court said that would be illegal.

"Definitely, we will arrest him if he attempts to walk again," Kaweesi said on Monday.

In power for 25 years, Museveni was initially credited with restoring the rule of law and fixing a broken economy but analysts and opposition politicians have since accused him of becoming increasingly autocratic and seeking to be president for life.

Museveni blames the high consumer prices on outside pressures.