A government decision to raise the price of bread this week from one Sudanese pound to three (from about two to six US cents) sparked protests across the country on Wednesday.
Eight demonstrators were killed in eastern Sudan on Thursday, officials said, during clashes with riot police on the second day of protests over the rising price of bread.
The protests spread on Thursday to the Sudanese capital Khartoum, where riot police fired tear gas to disperse demonstrators near the presidential palace, witnesses said.
"Six were killed and a number of people were wounded" in the eastern city of Al Qadarif, Al Tayeb al Amine Tah told local broadcaster Sudania 24, without providing further details.
The toll included a university student whose death during demonstrations in Al Qadarif had been reported earlier in the day.
"The situation in Al Qadarif is out of control and the student Moayed Ahmad Mahmoud was killed," said Mubarak al-Nur, a lawmaker in the city 550 kilometres (340 miles) from Khartoum.
Nur called on authorities "not to use force against demonstrators, who are asked to peacefully exercise their right" to protest.
Two other protesters were killed in the city of Atbara, around 400 kilometres east of Khartoum, governorate spokesman Ibrahim Mukhtar said.
Police in Atbara fired tear gas to disperse protesters just hours after authorities imposed a curfew on the city because demonstrators had torched the headquarters of President Omar al Bashir's National Congress Party (NCP).
Angry protesters on Thursday set fire NCP headquarters in two other locations, witnesses said
Demonstrators in Al-Qadarif "threw stones at banks (in the city centre) and smashed cars," resident Tayeb Omar Bashir told AFP by phone.
'Torched it completely'
They then "moved to the ruling party headquarters near the market and torched it completely", he added.
Demonstrators then moved towards the police station where they called for "freedom" and chanted "the people want the fall of the regime".
Protests in Dongola, 500 kilometres north of Khartoum, "started with university students who were joined by others when they reached the city centre", an eyewitness told AFP by phone.
"They attacked the headquarters of the NCP and set it ablaze," the witness said.
In Atbara, "some 1,500 demonstrators tried to enter the city (from a suburb) calling for the fall of the regime," an eyewitness said.
"Riot police intercepted them and fired tear gas at them," the witness added.
The demonstrations stopped in most cities as night fell and curfews came into force, the authorities said, but witnesses said they continued in Khartoum.
The bread shortage has hit Sudan's cities for the past three weeks, including the capital.
In the past year, the cost of some commodities has more than doubled in Sudan, where inflation is running at close to 70 percent and the pound has plunged in value.
Sporadic protests broke out in January this year over the rising cost of food, but they were soon brought under control with the arrest of opposition leaders and activists.
Sudan had significant oil reserves until South Sudan gained independence in 2011, and the north-south split saw the country lose three quarters of its reserves.