Sudan's former President Omar al-Bashir has been moved to Kobar maximum security prison, days after he was deposed in a military coup.
Reports say the ex-leader has until now been detained at the presidential residence under heavy guard.
He is reportedly being held in solitary confinement and is surrounded by tight security.
Months of protests in Sudan led to the ousting and arrest of the long-time ruler on Thursday.
Uganda's Minister for Foreign Affairs Henry Oryem Okello told Reuters news agency the country would consider offering the deposed leader asylum if he applied, despite an arrest warrant issued by the International Criminal Court (ICC).
As an ICC member, Uganda would have to hand over Mr Bashir if he arrived in the country. The ICC has not yet commented.
Until now, Mr Bashir's whereabouts since his removal were unknown. The coup leader at the time, Awad Ibn Auf, said Mr Bashir was being detained in a "safe place". He himself stood down soon afterwards.
Lt Gen Abdel Fattah Abdelrahman Burhan was then named as head of the transitional military council, to become Sudan's third leader in as many days.
Demonstrators have vowed to stay on the streets until there is an immediate move to civilian rule.
Protesters show calm conviction
By Joe Inwood, BBC News, Khartoum
A sea of doctors, shouting with such anger and passion that their voices crack. Thousands are still protesting outside the military institutions that for 30 years sustained the brutal regime of President Bashir.
Now, the military council that deposed him is struggling to maintain an increasingly fragile grip on power, while the man who once led the country sits in prison.
Today it has emerged he is in solitary confinement, locked in the very place where so many of his victims were held, tortured and killed.
Ordinary people have managed to bring an entrenched and violent regime to its knees. They have done it not through force of arms, but through calm conviction, passion and a dedication to their cause that you can see in their eyes.
Who is Omar al-Bashir?
Mr Bashir led Sudan for close to 30 years.
He is accused of organising war crimes and crimes against humanity in Sudan's western Darfur region, for which the ICC issued an arrest warrant.
After months of protests - starting in response to a rise in living costs and morphing into calls for the government to resign - Sudan's military toppled Mr Bashir in a coup on Thursday.
The transitional military council was set up in the wake of his removal, and has said it will stay in place for a maximum of two years until a civilian government can be put in place.
What are conditions like in the prison?
Kober prison, situated on the east bank of the Blue Nile, was built during Britain's near 60-year colonial rule of Sudan.
The building, built with bricks and surrounded by towering concrete walls, has the capacity to hold hundreds of prisoners. Space in its tiny cells, however, is said to be scarce.
Many of the protesters and opposition leaders who took to the streets demanding Mr Bashir's resignation have been detained on its special wing for political prisoners.
Sudan's feared National Intelligence and Security Service runs this wing, not the police.
Sudan analyst Alex de Waal, who has visited the prison, told the BBC its infrastructure has not been updated since it was built.
"The cells are very rudimentary, it is a very basic form of accommodation, there is no air conditioning or running water," he said.
Nevertheless, the prison has a reputation for treating the inmates well and not subjecting them to random violence, he added.
A former detainee at the prison told AFP news agency that up to seven prisoners, most of whom are petty criminals, are typically housed in each cell.
"There is a bathroom in each cell but no beds - only mattresses and mosquitoes," the former inmate, who was jailed there during protests against Mr Bashir's rule in January last year, said.
What's the latest with the protesters?
Demonstrators remain camped out the military headquarters in the Sudanese capital, Khartoum.
Reports on Monday said there had been efforts to disperse a sit-in, but protesters joined hands and troops stepped back from a confrontation.
The Sudanese Professionals' Association (SPA), which has spearheaded the protests, urged supporters to stop efforts to disperse them, calling on demonstrators to "protect your revolution and your accomplishments".
An SPA spokesman told the BBC that the group "completely rejected" the transitional military council leading the country, and said protesters seek the dismantling of state intelligence agencies and the "full dissolution of the deep state".
What has the military said?
Military council spokesman Maj Gen Shams Ad-din Shanto announced a raft of new measures on Sunday, including the end of censorship and new heads of the security forces.
The council has arrested former government members, he said, and will put in place whatever civilian government and whichever prime minister opposition groups agree.
But while the council promised not to remove protesters from their sit-in, the major also called on them to stop unauthorised roadblocks and "let normal life resume".
"Taking up arms will not be tolerated," he added.