Thousands of people have rallied in and around Sudan's capital, Khartoum, in a fifth day of protests against the government's decision to cut back fuel subsidies.
In Khartoum's twin city of Omdurman, a group of at least 2,000 protesters defied a heavy security presence, including army trucks parked on the street, to march after weekly Muslim prayers.
Smaller protests took place in Khartoum and other cities. Police fired tear gas to disperse some of the rallies.
Rights groups accuse the government of shooting dead 50 people since the protests began earlier in the week.
Authorities said Friday that they have arrested 600 people this week. Officials have also shut down the Khartoum offices of the satellite television channels Al-Arabiya and Sky News Arabia.
The U.S. State Department Friday condemned what it called "Sudan's brutal crackdown on protesters."
Spokeswoman Jen Psaki called the Sudanese approach "heavy handed" and "disproportionate."
The protests have become one of the biggest challenges to President Omar al-Bashir's government since he seized power in 1989.
Amnesty International and the African Center for Peace Studies urged the government to halt violence against demonstrators.
The government decision to cut subsidies caused a sharp rise in fuel prices, a development that angered many.
Sudan's fuel crisis began after South Sudan became independent in 2011. The new nation took over about three-quarters of Sudan's crude oil production.