Several demonstrations took place on Friday in Sudanese cities and states against violations by the Rapid Support Forces, which clashed with the Central Reserve Forces of the Sudanese police, in the first clashes of its kind between the two sides since the outbreak of battles.

Dozens of Sudanese demonstrated in the areas of al-Kalakla south of Khartoum and al-Wadi Street north of Omdurman, chanting slogans including "One people... One Army."

Protests also erupted in Kosti, the largest city in White Nile state, 350 kilometres south of the capital, after calls circulated on social media for the Rapid Support Forces to be removed from homes they had seized.

Many social media users promoted the demonstrations under the name "Friday of Rage".

Meanwhile, residents in central Omdurman, west of Khartoum, told AFP that clashes with various types of weapons took place in the Doha neighbourhood.

In El-Obeid, the capital of North Kordofan state, Al Jazeera correspondent reported one dead and 6 wounded in clashes today between the Rapid Support and the Central Reserve Forces, affiliated with the Sudanese police, in the first clashes of its kind between the two sides since the outbreak of fighting in the country.

Al Jazeera correspondent also reported that warplanes flew over the capital, in conjunction with gunfire southwest of Omdurman, and that the Sudanese army bombed positions of the Rapid Support Forces in the two areas.

Battles between the army led by Abdel Fattah al-Burhan and the Rapid Support Forces led by Mohamed Hamdan Daglo (Hemedti) have been taking place since April 15, and have so far killed more than two thousand, according to estimates that experts say are much underestimated.

The number of displaced people has reached two million across Sudan, according to the United Nations High Commissioner for Refugees, and the International Organization for Migration counted the flight of about 600,<> Sudanese to neighboring countries.

The fighting is largely concentrated in the capital and the western region of Darfur, but on Wednesday the army accused a rebel group of attacking its forces in South Kordofan state, hundreds of kilometres southwest of Khartoum.

A 72-hour truce agreed between the two sides with U.S.-Saudi mediation ended on Wednesday morning.

U.S. Assistant Secretary of State for African Affairs Molly Fei said on Thursday: "Yesterday we postponed the talks because the format was not the way we wanted."

"The ceasefire has not been fully effective, although it has allowed the transfer of important and urgent humanitarian aid," she told the House Foreign Affairs Committee.

Restrictions on Aid

On the other hand, the United Nations has warned that the conflict has taken on an ethnic dimension in the Darfur region, which is inhabited by Arab and non-Arab tribes.

The WHO confirmed on Wednesday that about two-thirds of health care facilities were out of service in Sudan's combat zones and warned that the risk of epidemics would increase with the rainy season that began this month.

Some 11 million people need health assistance, she said, expressing concern about attempts to control ongoing measles, malaria and dengue epidemics.

At a meeting in Geneva on Monday, the international community pledged $1.5 billion in aid, half of what humanitarian organizations need according to their field estimates.

But NGOs say they are still waiting to be able to work, and William Carter, director of the Norwegian Refugee Council in Sudan, said millions of people could not be helped because of severe restrictions on access for humanitarian workers and aid.

25 million people, more than half of Sudan's population, depend on humanitarian aid in a country that is sinking into destruction and violence at an "unprecedented" speed, according to the United Nations.