Sudan's main paramilitary group clashes with the army in apparent coup attempt.

Reuters Sudan's main paramilitary group said it seized the presidential palace, the army chief's residence and Khartoum's international airport on Saturday in an apparent coup attempt, but the military said it was fighting back.

The Rapid Support Forces (RSF), which accused the Army of attacking them first, also said they had seized the airfields in the northern city of Merowe and in El-Obeid in the west.

The situation on the ground was unclear. The army said it was fighting RSF in locations that the paramilitaries claimed to have taken. The army also said it had taken some RSF bases and denied that RSF had taken Merowe airport.

A major confrontation between RSF and the army could plunge Sudan into widespread conflict as it grapples with economic collapse and tribal violence, and could also derail efforts to move towards elections.

The clashes follow growing tensions between the army and RSF over the integration of RSF into the armed forces and who should oversee the process. The disagreement has delayed the signing of an internationally supported agreement with political parties on the transition to democracy.

The civilian forces that signed a preliminary version of this agreement in December called on Saturday for an immediate cessation of hostilities by both the army and RSF, to prevent Sudan from sliding towards "the precipice of total collapse".

"This is a crucial moment in our country's history," they said in a statement. "This is a war that no one will win and that will destroy our country forever."

Reporters Without Borders (RSF) accused the army of carrying out a conspiracy by supporters of former President Omar Hassan al-Bashir – who was deposed in 2019 – and of attempting a coup.

Reporters Without Borders (RSF) is headed by the former militia leader, General Mohamed Hamdan Dagalo, better known as Hemedti. He has been the deputy leader of the Sudanese Sovereign Council, led by army general Abdel Fattah al-Burhan, since 2019.

The army said the Sudanese air force was conducting operations against RSF. Images from broadcasters showed a military aircraft in the sky above Khartoum, but Reuters could not independently verify the material.

Gunfire could be heard in various parts of Khartoum, and eyewitnesses reported shootings in neighboring towns.

A Reuters journalist saw cannons and armored vehicles positioned on the streets of the capital and heard heavy gunfire near the army headquarters and RSF headquarters.

TV images showed smoke rising in several areas of Khartoum.

Doctors said that at least three civilians were killed.

Clashes also occurred at the headquarters of Sudan's state television, said an anchor who appeared on screen.

Sudanese military spokesman Mubasher told Al Jazeera television that the army would respond to any "irresponsible" action, as its forces have clashed with RSF in Khartoum and other parts of the country.

Brigadier General Nabil Abdallah said there was a strong presence of RSF troops at the TV station's headquarters in Khartoum.

Eyewitnesses reported gunfire in many other parts of the country outside the capital. This included intense exchanges of fire in Merowe, eyewitnesses told Reuters.

Eyewitnesses said clashes also broke out between RSF and the army in the towns of El Fasher and Nyala in Darfur.

International powers – the United States, Russia, Egypt, Saudi Arabia, the United Nations, and the European Union – called for an end to hostilities.

The army said that RSF tried to attack its troops in several positions.

RSF, which analysts say has 100.000 men, said its forces were attacked first by the army, stating in a communiqué on Saturday that the army surrounded one of its bases and opened fire with heavy weapons.

Hemedti's RSF evolved from the so-called Janjaweed militias that fought in a conflict in the 2000s in the Darfur region. An estimated 2,5 million people were displaced and 300.000 were killed in the conflict.

Prosecutors at the International Criminal Court have accused government officials and Janjaweed commanders of genocide, war crimes, and crimes against humanity in Darfur.

Hemedti positioned himself at the forefront of a planned transition to democracy, unsettling other military rulers and triggering a mobilization of troops in the capital Khartoum.

The division between the forces came to light on Thursday, when the army said that Recent RSF movements, particularly in Merowe, were illegal.

Reporters Without Borders (RSF), which together with the army overthrew Bashir four years ago, began redeploying units in Khartoum and elsewhere amid negotiations last month about their integration into the armed forces under a transition plan that would lead to new elections.