Sudanese troops on Thursday chased rebels in the country's troubled Darfur region, the army said, in renewed fighting that adds to a surge in violence outlined by the region's top peacekeeper.

The latest unrest in southeastern Darfur is an offshoot of battles between the army and Justice and Equality Movement (JEM) rebels earlier in the week, just across the border in South Kordofan state, said Sawarmi Khaled Saad, the Sudanese army spokesman.

Two alleged anti-regime activists in Sudan face up to 10 years' prison after a judge charged them on Wednesday in a terrorism-linked conspiracy over Arab Spring-style discontent sparked by inflation.

Rudwan Daoud and Ahmed Ali each face several accusations but the most serious is involvement with a terrorist or criminal organization, their lawyer Khaled Awad said outside the court.

Darfur rebels wounded in the latest fighting with Sudanese troops have gone to South Sudan for treatment, the army said on Tuesday, as Khartoum pushes Juba to end what is says is its backing for rebels.

The army and insurgents gave conflicting accounts of Monday's fighting, which came while Sudanese negotiators at fragile peace talks in Addis Ababa turned down South Sudan's proposal for settling oil fees and other critical issues by a United Nations-imposed deadline of August 2.

Top negotiators from Sudan and rival South Sudan have met in the latest round of African Union mediated talks to resolve bitter dispute, officials said Monday.

"Yesterday we had a meeting, and we tabled our positions," said Atif Kiir, a spokesman for Juba's delegation.

Protests which began more than a month ago in Sudan are ridiculously small, linked to opposition political parties and amount to nothing, a senior ruling party official said on Monday.

In an interview with Agence France Presse, Rabbie Abdelatti Ebaid of the National Congress Party denied demonstrations have been peaceful and he defended freedom of expression in the country despite concerns raised by Western governments and rights groups over a clampdown on demonstrators and journalists.

The current crisis in Mali is one of the most serious challenges facing the continent, the head of the African Union commission Jean Ping told a meeting of heads of state here.

"The situation in Mali is one of the most serious situations our continent is confronted with," Ping said at the opening of a closed door meeting on Mali and on tensions between Sudan and South Sudan.

More than 30 people were arrested on Friday when police fired tear gas at a mosque which has become a focus of Arab Spring-style protests in Sudan, a senior opposition figure said.

About 200 people were left inside the besieged Wad Nubawi mosque after many others fled from the tear gas, said Mariam al-Mahdi, a politburo member of the Umma party linked to the mosque in Khartoum's twin city of Omdurman.

South Sudan has put aside dire warnings over the stability and economic viability of the fledgling nation, the world's newest, to celebrate its first year of independence.

Crowds took to the streets of the capital Juba on Monday, with people crammed into cars driving around the city and honking horns to mark the first anniversary since separating from former civil war foes Sudan.

Sudanese security forces fired tear gas on Sunday after demonstrations broke out at the University of Khartoum, where nationwide protests against high prices began last month, a witness said.

"There are some demonstrations in the main campus," and authorities used gas to try to clear the area, he said, asking not to be identified.

Activists, politicians and students were among many people arrested during the latest anti-regime demonstrations in Sudan, a rights group said on Saturday.

The arrests came on Friday after police fired tear gas and rubber bullets at protesters who gathered at mosques, said the Organization for Defense of Rights and Freedoms, representing political, media, trade union and other activists promoting human rights.