Khartoum, Sudan (CNN) -- Sudanese took to the streets Friday in a fourth week of protests against rising prices and called for the ousting of the government.
"The people want to bring down the regime!" they shouted as they left the Imam Abd al-Rahman al-Mahdi Mosque after Friday prayers in the Omdurman neighborhood of Wad Nubawi, across the Nile from the capital of Khartoum.
Anti-riot police responded with tear gas, and plainclothes security officers arrested a number of protesters.
"I saw protesters throw rocks at the police, who responded with tear gas," a witness told CNN.
"There is heavy police and security presence, and they are chasing people into the allies of Wad Nubawi," he added.
The Imam Abd al-Rahman al-Mahdi Mosque, which is connected to the Ansar sect and the opposition National Ummah Party, has become a center for protests on Fridays after prayers for the past three weeks.
Activists dubbed Friday's day of action "Kandaka Friday" to honor Sudanese women. "Kandaka," or "Candace," was the title of ancient Sudanese Nubian queens.
Activist social media sites have reported protests in other Sudanese towns, including Khartoum North, El Obeid and Um Ruwwaba.
Al-Sir Ahmad Umar, a Sudanese police representative, said that "there was no confrontation with the police" during protests at the Imam Abd al-Rahman al-Mahdi Mosque and that "only a limited number" of protesters reached the main street.
He also said that the protest in the town of El Obied was limited to 20 people. "Do you call that a protest?" he said.
Activists say that 2,000 protesters have been arrested so far. This week, Human Rights Watch and Amnesty International issued a statement condemning the arrest and detention of protesters.
"Amnesty International and Human Rights Watch also urged the immediate and unconditional release of anyone arrested for participating in peaceful protests," the groups said.
The current wave of protests was started on June 16 by students at the University of Khartoum against government economic austerity measures that have increased fuel and food prices. Protests have spread into neighborhoods in the greater Khartoum area and other Sudanese cities.
Sudan's economy has suffered since the separation of South Sudan last year, which took with it nearly 75% of the country's oil wealth. While most of the oil wells are in the south, the pipelines and port to export the oil are in the north. The countries have not been able to agree on how to share oil revenues.
Sudanese President Omar al-Bashir has repeatedly downplayed the effect of the recent protests, calling the protesters "agitators" and "vagabonds."
"Those speaking of an Arab Spring in Sudan, we have a very hot summer here that will burn the enemies of Sudan!" he said Wednesday to crowds at the opening of a sugar factory.
Most of the protests have been scattered and relatively small, with participants in the hundreds. But Sudanese in the past have brought down two military governments through popular protest, in 1964 and in 1985.