Seven demonstrators were killed in Khartoum and its sister city Omdurman Wednesday as protests over the Sudanese government's scrapping of fuel subsidies raged for a third day, witnesses and relatives said.
The protests, which have now cost the lives of 10 people, have escalated into the worst in Sudan since President Omar al-Bashir seized power in 1989.
The US embassy called on everyone to avoid violence, saying it had received "regrettable" reports of casualties in demonstrations and warning Americans of the danger of further protests.
Riots broke out in several districts of the capital Wednesday, some of them near the centre, and public transport ground to a halt, an AFP correspondent reported.
"Freedom, freedom," and "The people want the fall of the regime," chanted the protesters, many of them students, borrowing the refrain of the Arab Spring protests which toppled several governments in 2011.
Police fired tear gas at stone-throwing demonstrators.
Shops were shut in Khartoum and Omdurman, with several roads cut by protesters who burnt tyres, sending black smoke billowing into the sky, and blocked access with tree trunks.
The education ministry said schools in the capital would remain shut until September 30.
The AFP correspondent reported several users saying Internet access had been cut, but it was not immediately known if this was a fault or a deliberate move by the authorities.
Vehicles were burned in the car park of a luxury hotel just 500 metres (yards) from Khartoum's international airport, and a petrol station in the area was also set alight.
Police made around 20 arrests and sealed off a section of the main road to the airport.
In Khartoum North, a witness said six cars were torched, as public transport across the capital ground to a halt. "Now I have to walk 10 kilometres (six miles)," said Ahmad Amer, on his way home from work.
Two people had already been killed in riots in the Khartoum area, police and the family of one of the victims said, and a third person was killed south of the capital on Monday.
Call for restraint
The US embassy urged restraint by all sides.
"We call on all sides not to resort to force and to respect civil liberties and the right to peaceful assembly," said an embassy statement issued in Arabic.
"In these difficult moments, it is necessary for all sides to show restraint and prudence."
The protests erupted in response to the government's announcement of steep price rises for petroleum products as it suspended subsidies in a bid to reform the economy.
On Tuesday, protesters ransacked and then torched offices of the ruling National Congress Party in Omdurman, witnesses said.
An AFP correspondent said around 1,000 demonstrators spilled into Omdurman's heavily populated Al-Thawra district and were confronted by anti-riot police.
The Omdurman protests lasted until around dawn on Wednesday.
One student was killed in Omdurman, named by his family as Omar Mohammed Ahmed al-Khidr. Police said that another man was killed in Khartoum, and that other civilians and police were injured.
"Most areas in Khartoum (province) saw unrest and unauthorised gatherings aimed at damaging property and allowing looting, necessitating police intervention," a statement said.
The protests first broke out in Wad Madani, in Gezira state south of Khartoum, scene of the first death on Monday. They have also spread to Nyala, capital of South Darfur state.
A Nyala resident told AFP by phone that thousands of students filled the streets of the city and blocked a main road.
Oil prices at the pump have shot up to 20.80 Sudanese pounds ($4.71) a gallon from 12.50 pounds ($2.83), while diesel has risen from 8.50 pounds a gallon to 13.90 pounds.
Inflation in Sudan is already running at 40 percent.
President Bashir said on Sunday the subsidies had reached "a level that is dangerous for the economy".
Sudan lost billions of dollars in oil receipts when South Sudan gained independence two years ago, taking with it about 75 percent of the formerly united country's crude production.
Since then Sudan has been plagued by inflation, a weakened currency and a severe shortage of dollars to pay for imports.