Live rounds and tear gas have been fired sporadically in Uganda's capital Kampala and other areas as military units and anti-riot police try to disperse demonstrations.
Protesters are unhappy about the arrests and alleged beatings of detained opposition legislators critical of President Yoweri Museveni.
Video footage showed demonstrators setting bonfires and barricades on Kampala's streets on Monday, and police and soldiers trying to remove the roadblocks.
Among those demonstrating were supporters of Robert Kyagulanyi, a pop star turned opposition parliamentarian, who goes by the stage name Bobi Wine. Kyagulanyi was arrested in the northwestern town of Arua last week.
Tensions have simmered in Uganda since Kyagulanyi and his colleagues were detained.
He was taken into custody on suspicion of taking part in the pelting of the presidential convoy with stones. The incident, which occurred during a parliamentary by-election campaign, left car windows smashed.
Museveni posted a statement on his Facebook page on Tuesday to justify the detention of the opposition politicians and their supporters.
"The problem in Arua was caused by Bobi Wine's group together with Kassiano Wadri, who attacked me, a useless action because I am protected and I can defend myself," Museveni said.
"The more serious issue is these chronically indisciplined people attacking women and children, destroying people's property, etc. Who is Bobi Wine or anybody to beat our people and for what?"
|Security forces have tried to contain demonstrations over the detention of opposition MPs [Ronald Kabuubi/AP]|
Kyagulanyi is seen by many as the new face of the opposition, barely a year after his entry into politics.
He has built a large youth following through his often biting criticism of Museveni's government, which he sometimes expresses through his music.
Kyagulanyi, 36, was elected to parliament last year and has since emerged as a powerful voice with his calls for young people to "stand up" and take over the East African country from what he calls the government's failed leadership.
Officials see his appeal as a threat to Museveni's hold on power, which is waning because of public anger over deteriorating public services, corruption, and rights abuses.
Many Ugandans have expressed concern for Kyagulanyi's safety after the country's deputy prime minister told legislators he had been hospitalised while in custody, without giving further details.
He has not been seen in public since he was detained, and the absence of news has spurred social media campaigns calling for his release.
Only a few members of his family and a handful of colleagues have been able to see him in custody. His brother Eddy Yawe told Al Jazeera the opposition politician is in bad health.
"When I met my brother, he could not walk, he was lifted up by two guys. He could not stand. He could barely breathe. He could not sit on his own," Yawe said.
"He had pain everywhere... He had lots of complications from [the] pains he was having in his stomach. He told me that they used an iron bar to hit his head, which made him fall down.
"He said as one man was breaking his finger, one was breaking a toe, another one was trying to extract his lips manually, one was pulling his ears and another one was holding his private parts and squeezing them to death.
"He collapsed and when he regained consciousness, he found himself locked up in some kind of container, chained up... He was all bloody and helpless."
The government has denied allegations of torture.
|Dozens of people have been arrested for protesting Bobi Wine's arrest [AP]|
The Ugandan government has been accused of stifling dissent through intimidation, beatings, detentions and prosecutions on trumped-up charges.
Kyagulanyi, who is being held at a military prison near Kampala, will appear in court on Thursday.
He, several MPs, and dozens of others have been charged with treason and illegal possession of firearms over their alleged role in the stoning of the president's convoy.
Medard Sseggona, a lawyer for the defendants, told Al Jazeera the politicians are innocent.
"The charges are not only laughable but ridiculous," Sseggona said.
Another 68 suspects arrested during two days of demonstrations across the country are also expected to appear in court, with the government not backing down on plans to proceed with prosecutions.
Museveni said the trial "should send a warning to those who are in the habit of miscalculating".
Opposition supporters see the alleged mistreatment of the detained as part of a pattern of repression by Museveni's security forces, an allegation the government denies.
A man was shot dead and five others wounded in anti-government protests in the town of Mityana.
"The police can use live bullets if they are not equipped with anti-riot equipment and the rioters are on the verge of killing innocent people. That is also possible," Museveni said.
But Kyagulanyi and his supporters are not giving up.
"He remains unshaken. He remains very strong in spirit, but weak in body. The body is definitely weak because he was really tortured but his spirit and will remain unshaken," Sseggona said.
"When you know that you are fighting corruption, you are fighting maladministration in your own country, you want to set the country free. It is quite a painful experience to be tortured for what you believe in," he added.
|President Museveni has been elected five times since he took power by force in 1986 [File: AP]|
President for life
Museveni seized power in 1986 and has since been elected five times. The last vote in 2016 was marred by allegations of fraud.
Critics say he is set to rule Uganda for life after parliament passed legislation last year removing a clause in the constitution that had prevented anyone over 75 from holding the presidency.
Museveni, 73, is now able to seek re-election in 2021. His supporters say he has held power for so long because of genuine mass support.
Although Museveni campaigned on his record of establishing peace and stability, some worry that is being eroded the longer he stays in power.
Previous attempts by an opposition leader, Kizza Besigye, to remove him from power were unsuccessful.
Museveni said any attempt by the opposition to cause further unrest will be stopped.
"Those who pretend to support the opposition are misleading them by failing to advise them to stop intimidating and attacking Ugandans. The Ugandans, led by us, will resist them," he said.
While Kyagulanyi has not made a public statement about his alleged abuse, his brother is convinced his position has not changed.
"He has already paid the cost of freedom. He told me he can die for this country," Yawe said.
|Bobi Wine gestures to supporters after being sworn in as an MP last year [Ronald Kabuubi/AP]|