Calls increased to find a solution to the widening conflict in Sudan with the approaching completion of its third month, while Human Rights Watch called on Tuesday the International Court of Justice to investigate "war crimes" committed in the Darfur region.

The Quartet of the Inter-Governmental Authority for Development in East Africa (IGAD) had called on the two parties to the conflict to conclude an "unconditional" ceasefire agreement, after the failure of several similar attempts over the past months.

The army boycotted the meeting, which was hosted by Addis Ababa, and reiterated its demand that Kenya be removed from the presidency of the committee, accusing it of "lack of neutrality" in the conflict.

Since its outbreak on April 15, battles have continued between the army, led by Abdel Fattah al-Burhan, and the Rapid Support Forces, led by Mohamed Hamdan Dagalo, with no prospect of calm. Experts believe that the two former allies chose to proceed with a war of attrition that would only stop with a military victory for one of them at the expense of the other, although no party has achieved significant gains since the start of the war that change the field data.

The US ambassador to Khartoum, John Godfrey, warned that "a military victory for either of the two conflicting parties ... will cause unacceptable human costs and damage to the country."

The diplomat, who left the Sudanese capital with the start of the fighting, like most foreigners, said in a statement that it was necessary to "reach a negotiated way out of the crisis."

He stressed that this cannot mean a return to "the status quo that existed before April 15," when Al-Burhan and Daglo seized the reins of power after overthrowing civilians in a military coup.

Godfrey's remarks came ahead of meetings expected to be held by US Assistant Secretary of State for African Affairs Molly in Addis Ababa on Tuesday, with Sudanese and regional officials.

These meetings come the day after a meeting held by the Quartet, consisting of Kenya, Djibouti, Ethiopia and South Sudan, to which the two parties to the conflict called. The army boycotted the meeting because of its failure to meet its demand to remove Kenya from chairing the committee, as it accuses her of supporting the Rapid Support Forces.

The IGAD committee called on the two parties to an unconditional cessation of hostilities, stressing that it would ask the African Union to discuss the possibility of deploying the East African Standby Force (ISAF) with the aim of "protecting civilians" and ensuring the arrival of aid.

In addition, Kenyan President William Ruto requested a "humanitarian zone with a diameter of 30 km around Khartoum to facilitate the arrival of humanitarian aid" needed by more than half of the country's population.

Mediation initiatives, whether from IGAD or others led by Washington and Riyadh, did not succeed in finding grounds for understanding.

And the United Nations warned at the end of last week that Sudan, one of the poorest countries in the world even before the outbreak of the current battles, is on the verge of a "comprehensive civil war" whose repercussions will affect the entire region.

The conflict has killed more than 2,800 people and forced more than 2.8 million people to flee, more than 600,000 of whom have sought refuge in neighboring countries, most notably Egypt and Chad, according to data from the International Organization for Migration.

The rest of the population, whose total number was estimated at about 45 million people before the start of the fighting, suffers from a lack of food, services and energy sources, while reports continue of cases of looting, sexual violence and the intensification of ethnic conflicts, especially in the Darfur region (west).

Over the past weeks, witnesses in Khartoum and Darfur have given horrific accounts to AFP of the abuses, accusing in particular the Support Forces and allied Arab groups of being behind them.

On Tuesday, Human Rights Watch reported that "several thousand Rapid Support fighters" and its allies attacked the town of Misteri in Darfur in late May.

In a lengthy report, she explained that they besieged the town, which has an estimated population of 46,000, using "motorcycles, horses and pick-up trucks," and opened fire on "those who tried to flee."

It quoted witnesses as saying that the attackers looted "all day long the residents' property, as they stole livestock, seeds, money, gold, phones, and furniture... After looting the houses, the attackers set them on fire."

It indicated that the attacking forces "executed at least 28 members of the Masalit ethnicity and killed and wounded dozens of civilians," one of the most prominent non-Arab ethnic groups in West Darfur.

The organization quoted witnesses as saying that the attackers "pursued people seeking safety in schools and the mosque," and "repeatedly attacked classrooms in search of men and carried out field executions against those they found."

The organization considered that "many of these violations committed in the context of the armed conflict in Sudan amount to war crimes," calling on the International Criminal Court to investigate these attacks.

"The mass killing of civilians and the complete destruction of the town of Misteri demonstrates the need for a stronger international response to the widening conflict," said Jean-Patset Gallupin, researcher at the organization.

The court is investigating grave violations committed in Darfur during a conflict that began in 2003 and spanned nearly two decades, leaving nearly 300,000 dead and 2.5 million people displaced, according to the United Nations.