Anti-government sentiments spilled over after Friday prayer sessions around Sudan's capital, Khartoum, in the most widespread protests yet against government spending cuts.
Entering into their sixth day, demonstrations spread into areas of the city where previous rallies held by student protesters had not taken place.
Riot police and activists clashed as tear gas and rocks were exchanged, witnesses told Reuters news agency.
Anti-government campaigners burned tyres, as police and security forces used batons to break up the demonstrators.
The government plans to cut spending across all areas, including decreasing fuel subsidies, to fill a budget deficit.
Soaring inflation has rocked the country since South Sudan seceded a year ago, taking with it three quarters of the country's oil resources. Processing and exporting facilities remain in the North.
Protests of this magnitude are rare in Sudan, a country that avoided the "Arab Spring" movement which swept through Egypt and Libya.
Sudan and South Sudan talks resume
As tensions boil over within the country, in-person talks between Sudan and South Sudan recommenced on Friday, with little advancement on the formation of a demilitarized buffer zone along the disputed border line, a chief mediator from Juba said.
South Sudan's foreign minister, Nhial Deng Nhial, told reporters, "We couldn't make any progress on the issue of the geographical extent of the safe and demilitarized border zone."
Talks were put on hold in early June after both sides failed to agree to a protected border region. In order for talks to progress, a spokesperson for Khartoum's delegation said the creation of an area along the border was crucial for the negotiations to progress, adding both sides were to continue discussions on Saturday.
"We will continue discussing this, which is really a thorny issue and which will need investment of all efforts to bridge the differences," Omer Dahab, spokesperson for the Khartoum delegation said.
Following weeks of violence along the disputed border, sparking fears of an all-out conflict, both Sudans met in Addis Ababa in May for the first in-person talks. Both sides failed to reach an amicable agreement.
The United Nations had given both countries until August 2 to resume talks about the border zone and oil sharing.
jlw/rc (AFP, Reuters, dpa)