The independent Sudan Tribune reported that Sudanese authorities used force when dispersing protests by university students in Khartoum and elsewhere.
The U.S. State Department said it documented "pre-publication censorship" on some of the country's independent newspapers.
"The United States is deeply concerned by the crackdown by the Sudanese authorities on peaceful demonstrators in Khartoum over the last three days," State Department spokeswoman Victoria Nuland said in a statement. "We call on the government of Sudan to respect the right of its citizens to freedoms of expression and peaceful assembly in order to raise their grievances."
Protests erupted after Sudanese authorities considered an austerity package aimed at easing budgetary strains. The Sudan Tribune reported that lawmakers passed a number of measures meant to cut state expenses, including a proposed end to fuel subsidies.
Sudanese President Omar al-Bashir had said some economic problems were tied to fighting with rebel forces along the border with South Sudan.
South Sudan gained independence last year under the terms of a peace deal with Khartoum. Ethnic tensions, oil disputes and border conflicts are threatening the peace.