Sudanese protesters march during a demonstration in the capital Khartoum. AP Photo

Khartoum - At least four protesters were killed and many injured by gunfire in the Sudanese city of Omdurman on Thursday, opposition medics said, as hundreds of thousands took to the streets to pile pressure on the country's military rulers.

Organisers had called for a million-person march in cities across Sudan in response to the killing of young protesters in El-Obeid, southwest of the capital Khartoum, earlier this week.

Thursday's killings, reported by the Central Committee of Sudan Doctors, one of the main protest groups, came as opposition leaders said there had been some progress in talks with the military on reaching a deal to form a new government after the ousting of long-time leader Omar al-Bashir.

Sudan has been gripped by months of political turmoil that climaxed in the army overthrowing Bashir in April. The opposition has kept up protests, pressing the army to hand over to civilians.

Despite signing a deal in July which secured a three-year transition period and a joint sovereign council with a rotating leadership, talks over the wording of a constitutional declaration on the changes have stumbled.

People demonstrate against the killing of protesting children, who were shot dead when security forces broke up a student protest in Khartoum. Picture: Mohamed Nureldin Abdallah/Reuters

"The agreement is really now just around the corner," Satea al-Hajj, a leader in the Forces of Freedom and Change (FFC) coalition of opposition groups, said in a press conference in Khartoum on Thursday.

Negotiations were set to restart later on Thursday, the spokesman for the military council said.

"IT'S TOO BAD"

The opposition had demanded that members of the sovereign council, which is intended to lead the country until elections are held, should not be granted blanket immunity from prosecution for past crimes. But FFC leaders said on Thursday they had agreed that they could be granted only 'procedural immunity' - meaning top officials could be tried with the permission of two-thirds of the legislative council.

Sudanese pro-democracy activists have posted videos on social media showing thousands of people taking to the streets in the capital, Khartoum. Picture: AP

The opposition leaders said both sides also agreed another key point, reaffirming that the parties included in the FFC would have 67% of the legislative council while the rest will be granted to other opposition and political groups.

Sudan's ruling military council did not immediately confirm the details of the agreements.

In Omdurman, across the Nile from Khartoum, protesters chanted "it's too bad, it's too bad, we don't have an army," expressing anger at the army for not protecting protesters.

Footage posted on social media also showed protests breaking out in El-Obeid, the state capital of North Kordofan state, and Wad Medani, the state capital of Jazeera state, southeast of the capital on the Blue Nile.

The Sudanese Professionals Association said the rallies are demanding justice for the killing of at least six people, including four students, earlier this week during student protests in a central province. AP Photo

The Sudanese Professionals Association, the main protest group and a leading voice in the FFC, had called for those responsible for Monday's killings in El-Obeid to be brought to justice.

The FFC accused military and paramilitary forces of firing on the high school pupils as they protested over bread and fuel shortages.

A senior army commander said a security force assigned to guard a bank was responsible for killing children protesting near there, the official SUNA news agency reported on Thursday. The bank guards were a government security force.

People demonstrate against the killing of protesting children, who were shot dead when security forces broke up a student protest in Khartoum. Picture: Mohamed Nureldin Abdallah/Reuters

Opposition groups have also accused the main paramilitary group, the Rapid Support Forces, of killing scores of protesters since Bashir was ousted and the RSF's role remains a point of contention.

The FFC said on Thursday that the RSF should be merged into the armed forces, a proposal opposed by Sudan's ruling generals, said al-Hajj.

Reuters