Nine days of country-wide protests against high prices in Sudan are no 'Arab Spring', President Omar al-Bashir said on Sunday, referring to a series of uprisings against regional strongmen.

"The people who burn the tyres are small in number and they are pushing for a fight," he told about 1,000 Sudanese students, suggesting that someone was behind protests in his country.

Anti-regime demonstrations have widened since Bashir on June 18 announced austerity measures including tax hikes and a phasing out of fuel subsidies to prop up the country's ailing finances.

"They said these economic measures would be a chance for an Arab Spring in Sudan. But the Arab Spring in Sudan happened many times already," he said, referring to previous uprisings by 'all' the country's people.

In 1964, protests led to a mass mobilisation that toppled the military dictatorship then in power.

But Bashir said he himself remains popular.

He said he took an 'open car' around Khartoum on Friday, when smoke hung over the city from burning tyres, as residents of many neighbourhoods clashed with police and denounced the regime and high food prices.

"When the people saw me they shouted 'Allahu akbar'," Bashir said.

The protests over rising prices started with students outside the University of Khartoum. But they broadened to include a cross-section of the population in numerous locations throughout the capital, and several other parts of the country.

On Sunday, lawyers opposed to food price inflation took to the streets near the courthouse in El Obeid, capital of North Kordofan state, where some were arrested, witnesses said.

Separately, about 100 students from a local university in El Obeid also protested and called for the downfall of the regime, while other demonstrators gathered in the town's main market, the witnesses said.

Police responded with tear gas and batons, they added, in what has become the standard reaction by security forces since demonstrations began on June 16 in Khartoum.

Bashir, an army officer who seized power on June 30, 1989, withstood earlier student-led protests by thousands of people objecting to high prices in 1994.

Though smaller in size, the current protests have occurred continuously for more than a week, with citizens blockading streets and throwing stones at police.

Witnesses on Sunday evening reported groups of about 100 people demonstrating in two areas of Khartoum.

Security forces in the Red Sea town of Port Sudan beat people who were about to protest there, arresting some, witnesses also reported.

State security officers ordered one of Sudan's main opposition parties, Umma, not to hold any public forums at its headquarters, a party leader said.

"We are going to discuss this in our political bureau and decide what do do," the party's general secretary, Ibrahim Al Amin, said.

Hundreds of people attended a forum over food prices at Umma's offices last week before their attempt to demonstrate was met with police tear gas.

Inflation has risen each month, hitting 30.4 per cent in May, before Finance Minister Ali Mahmud al-Rasul on Wednesday announced a jump of about 50 per cent in the price of petrol.

Bankrupt Sudan has lost billions of dollars in oil receipts since South Sudan gained independence last July, leaving the north struggling for revenue, plagued by inflation, and with a severe shortage of dollars to pay for imports.

The country's poverty rate is 46.5 per cent, the United Nations says.

Sudan's demonstrations remain small compared with the mass uprisings that swept some Middle East countries last year as part of the Arab Spring protests.