Sudanese protesters have taken to the streets in growing numbers through the week and further demonstrations are expected in what activists have called "the Sudan revolts".
Violence escalated across the capital Khartoum on 21 June, as riot police fired teargas at protesters, while pro-regime groups, armed with machetes and swords, attacked protesters, the protesters said.
Police denied violence had been used against demonstrators.
Saata Ahmed al-Haj, head of the opposition Sudanese Commission for Defence of Freedoms and Rights, said hundreds of protesters have been detained over the past five days - since president Omar al-Bashir announced a new austerity plan.
Al-Hadj said that even though most of them were later released, they had been mistreated while in detention.
He accused the security forces of shaving protesters' hair, stripping them naked, flogging them and leaving them outside in the sun for hours.
"I am under house arrest along with several opposition members and security forces are encircling the place," he said. "Our 'offence' is we are searching for freedom and this is a crime in Sudan," he told AP.
"This is the outcome of political, economic and military suffocation felt by people here," he added.
Crackdown against students and journalists
Police also stormed several universities where students were holding protests, in which they called for a regime change in response to the government's economic policies and widespread corruption.
Across the capital, hundreds of students demonstrated and set up road blocks on the routes leading to their campus.
Witnesses said police and pro-regime militia stormed the campuses, dispersing the protesters and beating up the remaining students.
At least seven students were injured in the attacks.
In a separate protest in the northern suburb of Bahri, women and girls also set up road blocks to protest against soaring food prices.
Salama el-Wardani, an Egyptian journalist who works for Bloomberg, told the Egyptian daily al-Masry al-Youm that she was detained and interrogated for five hours along with a Sudanese activist, Maha al-Senousi.
They were arrested while covering protests at Khartoum University on 22 June.
El-Wardani is now reportedly under house arrest and could be deported. A reporter with the AFP news agency has also been detained.
The country's economic situation has been deteriorating since South Sudan gained independence a year ago, following a peace deal that was struck in 2005, which ended decades of civil war.
With the two countries fighting over oil resources and unable to reach a lasting agreement, South Sudan shut down its production in January.
Oil was previously Sudan's main source of state revenue and foreign currency. Since South Sudan stopped production, the currency has depreciated, coupled with rising prices for food and imported goods.
The finance minister recently announced a series of austerity measures, which include government cuts, fewer fuel subsidies and tax increases, provoking widespread unrest.