Sudanese police fired tear gas at scores of student protesters in the east of the country witnesses said, as unrest provoked by tough austerity measures stretched into a second week.

Street protests have spread throughout Sudan for more than a week since the government announced it would impose spending cuts to stabilise Sudan's economy, which has deteriorated since the secession last year of its oil-producing south.

The most widespread demonstrations occurred on Friday when protests expanded beyond a core of students into various parts of the capital Khartoum, triggering a security crackdown, Reuters reports.

Khartoum has been quieter since Saturday, but small demonstrations have continued in other cities.

On Wednesday, over 100 student protesters gathered outside the university in the city of Kassala near the border with Eritrea shouting "No, no to high prices" and "the people want to overthrow the regime", two witnesses said.

Police fired tear gas at the students, who threw rocks at the security forces, they added. Police did not immediately comment on the incident but have repeatedly denied using excessive force against demonstrators.

On Tuesday night, police also used tear gas and batons to disperse about 100 demonstrators in the Nile river town of Atbara, witnesses said. Earlier on Tuesday, Salma El Wardany, a reporter for Bloomberg news agency who is an Egyptian citizen, said she had been expelled from Sudan for covering the protests.

There was no immediate comment from the security services.

The protests have been widely scattered and never mustered more than a few hundred people at a time. Sudanese officials have played them down, saying they will press on with austerity steps they see as necessary to heal the economy.

Sudanese finances were hit hard when oil-producing South Sudan declared independence a year ago. Crude production had provided most of the sprawling northeast African state's revenues and exports.

The loss of foreign currency inflows has weakened the Sudanese pound and this has fuelled sharp rises in the price of food and other goods, many of which are imported.

The United States has condemned what it described as Sudan's "heavy-handed approach" to the demonstrations.