Sudanese police have fired tear gas to disperse hundreds of protesters outside a mosque belonging to an opposition party in the capital Khartoum, a witness has said.
The witness said on Friday that demonstrators carried Sudanese flags and banners reading "The people want the regime to fall", a slogan used by protesters during the Arab Spring uprisings over the past year.
The protesters had gathered in the capital's Hijra Square beside the mosque of the opposition Umma party. After the tear gas and an unknown number of arrests, demonstrators burned tyres and threw stones at police before running for cover, the witness told the AFP news agency.
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"Police have fired tear gas at protesters as they attempted to take to the streets following Friday prayers. There is a lot of defiance here, protesters have blocked the roads and they are burning tyres," said Al Jazeera's Zeina Khodr, reporting from Khartoum.
"People have been chanting 'We want the downfall of the government', so people here belive that this is the start of their revolution," she added.
Waffa al-Amin, an activist, told Al Jazeera by phone from the protests that "about 2,000" protesters had gathered in the Ummdurman district of the capital.
"We are surrounded by 500 police and security forces. We have blocked the area so they can't get to us, however, they have been firing tear gas at us," al-Amin said.
Demonstrators planned major protests for Friday and Saturday, the 23rd anniversary of a coup by President Omar al-Bashir.
Some have dubbed this Friday the "Licking the elbow" protest, a phrase used Sudanese to mean attempting the impossible.
The UN human rights chief has urged the Sudanese government to avoid "heavy-handed suppression".
"Tear gas, rubber bullets, live ammunition and other heavy-handed suppression will not resolve the frustrations and grievances of the people, said Navi Pillay, UN high commissioner for human rights, in a statement on Thursday.
Rights groups say scores of people have been arrested since protests against inflation began on June 16 in Khartoum.
Human Rights Watch said the government was also using the protests "to silence dissenters".
After Bashir announced austerity measures, including tax hikes and an end to cheap fuel, the protests spread to include a cross-section of people in numerous locations throughout the capital and other parts of Sudan.
Bashir, suggesting that someone was behind the disturbances, has called them small-scale and not comparable to the Arab Spring uprisings in Egypt and elsewhere. He maintains that he remains popular.
For more than a week, demonstrators in groups of 100 or 200 have burned tyres, thrown stones and blocked roads, while calling for a change in government.
"After 23 years of endurance, the Sudanese people have decided to say enough is enough," said an activist from the movement Sudan Change Now.
The protests, which started as mainly student-driven demonstrations on university campuses and remain small, also
spread beyond Khartoum.
One broke out in North Kordofan province in western Sudan where about 200 protesters chanted "No, no to high prices" and another in Wad Madani, capital of al-Jazira province near Khartoum, according to witnesses.
Police used teargas and batons to disperse the crowds in Wad Madani protesting against high prices. Kassala, a city in eastern Sudan, also saw a small protest.
It is not yet clear whether the protests pose a real threat to the ruling National Congress Party and Bashir, but the tough response by security forces shows how high the stakes are for Sudan's leaders who are struggling to contain multiple armed rebellions as well as the economic crisis.
Sudan has suffered soaring inflation since South Sudan seceded a year ago, taking with it about three quarters of the country's oil, and activists have been trying to use public frustration to build a movement to topple Bashir's government.
Large demonstrations have been relatively rare in Sudan, although Sudan saw popular revolts in 1964 and 1985, and
security forces move quickly to disperse protests.
Coverage of protests in local media has been restricted and scores have been arrested, activists and opposition groups say.
Bashir has dismissed the protesters as a handful of agitators whose aims most Sudanese reject.
Bashir is a former army officer who seized power in 1989.