Global advocacy group Amnesty International says more than 200 people were arrested during a public demonstration Monday in Khartoum. Protests broke out across southern Sudan following reports senior officials of the South's ruling party had been detained.
Amnesty International condemned what they called a "violent crackdown" against the political demonstrators.
Researcher Rania Rajji says the use of torture on the detainees is especially troubling.
"Our concern is there is the right of people to hold a peaceful demonstration. They seem not to have broken any Sudanese laws, so they are allowed to their freedom of expression and to peacefully demonstrate," said Rajji. "On the other hand, [our concern is] the use of violence during the arrests but also the extended use of violence, torture, and other forms of ill-treatment during detention."
Senior members of the South's Sudan People's Liberation Movement, including the secretary general Pagan Amum and his northern deputy Yasir Arman, as well as key members of northern opposition groups, were among those picked up by authorities.
The detainees were later released, but news of the government actions triggered unrest in southern Sudan.
The offices for the National Congress Party - the party headed by Sudanese President Omar Hassan al-Bashir - were reportedly attacked in the southern cities of Wau and Rumbek, as well as in the Tur-Alei county in Warrap state. Some NCP officials operating in the South had to flee to safety.
Monday, the leader of Southern Sudan, Salva Kiir, tried to alleviate fears that the recent outburst of unrest would result in a re-ignition of conflict.
"This [detainment] prompted us to call for an emergency meeting of the SPLM leadership, where it was resolved that the situation must be contained," said Kiir. "The SPLM leadership also resolved to use all the necessary means to ensure that the country does not resort to war again."
The NCP has been relatively quiet about the crackdown, but the Sudanese foreign minister summoned foreign envoys to brief them that the rally was held illegally, forcing the state to act.
The protest demonstration was called by a joint alliance of northern opposition groups and the SPLM, who in September this year met in Juba to agree to a unifying set of principles. Reports indicate the parties are considering uniting under a single candidate to oppose President Bashir in the polls.
The alliance is protesting the continued delays in the process of reforming national security laws, which it says gives undue powers to the state's security teams. They are threatening to boycott the upcoming elections, which they say can not be free and fair unless the laws are amended.
SPLM is also protesting the stalled negotiations over a referendum law that codifies a Southern independence vote now scheduled for January 2011.
The upcoming national elections were agreed to as a provision in the historic 2005 Comprehensive Peace Agreement that ended the decades-long civil war between the North and South. An estimated 1.9 million people were killed during the conflict, most of them Southerners.