NYALA (Sudan) - Sudanese protesters called for justice on Wednesday, after at least eight people died in violence unprecedented since Arab Spring-style demonstrations began in mid-June, witnesses said.

The mostly youthful protesters gathered in Nyala, the capital of South Darfur state, to vent their anger after the killings during a much larger protest on Tuesday sparked by high prices, the witnesses said.

"We want justice," they shouted. "We want retribution."

Police fired tear gas and the sound of gunfire was heard but there were no apparent injuries, the witnesses said, adding protesters set tyres alight in the streets.

They called for the overthrow of the state governor and of the government in Khartoum after the first officially confirmed deaths related to scattered anti-regime protests, which have taken place around Sudan for more than six weeks.

"Eight citizens were killed and 24 injured, including three police who are in a serious condition," the official SUNA news agency quoted police as saying.

An activist youth movement, Sudan Change Now, accused security forces of firing live ammunition and said 12 citizens, many of them young people, were killed.

Police did not give the cause of death but said officers used a "low level of force" to control the situation after demonstrators burned a petrol station and police facilities in Nyala.

The demonstrators had stoned government buildings and burned tyres during Tuesday's rally, a witness said.

Bothina Mohammed Ahmed, spokeswoman for the South Darfur government, said Tuesday's demonstration started because students "rejected the price of transport announced by the government."

She added that "other groups" whom she did not identify attacked government property during the protest.

Demonstrations in Sudan began last month when University of Khartoum students voiced opposition to high food prices, starting the longest-running public challenge to the 23-year regime of President Omar al-Bashir.

Inflation reached 37 percent year-on-year in June and jumped almost 10 points in May.

After Bashir announced austerity measures, including tax hikes and an end to cheap fuel, scattered youth-driven protests spread to include a cross-section of people, often in groups of 100 or 200, around Khartoum and in other parts of Sudan.

Protests have dwindled during the Muslim holy month of Ramadan, which began on July 20.

But a strike by public transport drivers upset over high fuel prices has added to the burden of Nyala residents.

Schools were closed on Wednesday, local radio announced. Police had been deployed across the city before the new demonstration erupted, a resident said.