Women and children rallied quietly outside Sudan's state security headquarters Thursday calling for the release of prisoners held in a crackdown after protests over fuel price hikes, an Agence France Presse reporter said.

The crowd of around 45 carried photographs of the detainees, including social media activist Dalia El Roubi and Amal Habani, a journalist with Al-Khartoum newspaper, the reporter said.

An African police adviser with the international peacekeeping mission in Sudan's Darfur region has died from wounds suffered in an ambush three months ago, the mission said on Tuesday.

The death of the Sierra Leonean brings to eight the number of peacekeepers killed in the July 13 attack north of the South Darfur state capital Nyala.

Female university students in Sudan protested for a second day running on Tuesday, their campus president said, on the ninth day of anti-government demonstrations that sparked a deadly crackdown last week.

The protest, with 100 students at most, was "on a smaller scale" than Monday's rally, Ahfad University for Women president Gasim Badri told Agence France Presse.

Sudan pointed to "fake" victim photos and foreign interference Monday as it defended a deadly crackdown on protesters, which drew fresh criticism from inside the ruling party as rallies continued.

With reporters complaining of stepped-up censorship, numerous videos and photographs purporting to show bloodied victims have circulated on YouTube, Facebook and other social media since the demonstrations began eight days ago, sparked by a rise in fuel prices.

A senior official in Sudan's ruling party on Monday spoke out against an "unnecessary" deadly crackdown on demonstrators protesting fuel price hikes, saying the government should have instead encouraged dialogue.

"The fact that so many have died points to the degree of violence," the official told Agence France Presse on condition of anonymity, in comments that reflect divisions within the governing National Congress Party (NCP).

Sudan vowed Sunday to stand firm on its decision to hike fuel prices, despite days of deadly protests and criticism from within the ruling party and from hardline Islamic leaders.

Authorities say 33 people have died since petrol and diesel prices jumped last Monday, sparking the worst protests in the history of President Omar al-Bashir's regime.

Sudan's foreign minister accused the United States Friday of denying a visa to President Omar al-Bashir, wanted on war crimes charges, barring him from taking part in a U.N. summit.

"It is with deep regret that I inform you of the refusal of the authorities of the United States, the host government, to give an entry visa to President Bashir and his delegation," Sudanese Foreign Minister Ali Karti told the U.N. General Assembly.

Two Arab tribes which have been battling off-and-on for months in Sudan's Darfur region have resumed clashes, leaving dozens dead, one of their leaders said on Friday.

"In total, 51 people were killed and 65 were injured," in fighting on Thursday, Ahmed Khiri, a Misseriya tribal leader, told Agence France Presse.

The United States on Friday blasted the "brutal crackdown" this week by the government of Sudan against protesters in Khartoum, calling it "heavy-handed" and "disproportionate."

Friday saw a fifth consecutive day of protests against fuel price hikes that have seen scores of demonstrators shot dead by government forces.

Sudan's interior ministry said Friday that 600 people had been arrested for their involvement in anti-government demonstrations that have rocked the country this week.

The people were "arrested for participating in acts of vandalism and will be judged next week," a ministry statement said.