(AFP) - Three civilians died in battles between Sudanese paramilitaries and the regular army, which said it launched air strikes against them, sparking global concern days after the army warned the country was at a "dangerous" turning point.

The paramilitaries said they were in control of the presidential place as well as Khartoum airport, claims denied by the army, as civilian leaders called for an immediate ceasefire to prevent the country's "total collapse".

The doctors' union reported the three civilian deaths, including at Khartoum airport which is in the city centre, and in North Kordofan state. At least nine others were wounded, the medics said.

The eruption of violence came after weeks of deepening tensions between military leader Abdel Fattah al-Burhan and his number two, paramilitary commander Mohamed Hamdan Daglo, over the planned integration of the paramilitary Rapid Support Forces (RSF) into the regular army.

That was a key element of talks to finalise a deal that would return the country to civilian rule and end the crisis sparked by their 2021 coup, which triggered a deepening economic crisis in what was already one of the world's poorest countries.

US Secretary of State Antony Blinken said he was "deeply concerned" and urged both sides to "stop the violence immediately", a call echoed by the United Nations, African Union, Arab League, regional bloc IGAD and the European Union.

Russia's foreign ministry said there was "serious concern in Moscow," which called for urgent steps toward a ceasefire.

The army said it had carried out air strikes and "destroyed" two RSF bases in Khartoum.

More than 120 civilians had already been killed in a crackdown on regular pro-democracy demonstrations since the coup.

- 'Sweeping attack' -

The RSF said its forces had taken control of Khartoum airport, after witnesses reported seeing truckloads of fighters entering the airport compound, as well as the presidential palace -- where Burhan is officially based -- and other key sites.

Its claims were quickly denied by the army, who said the airport and other bases remain under their "full control", publishing a photograph of black smoke billowing from what it said was the RSF headquarters.

The army also accused the paramilitaries of burning civilian airliners at the airport, and Saudi flag carrier Saudia said it had suspended all flights to and from Sudan until further notice after one of its Airbus A330 planes "was involved in an accident".

RSF chief Daglo vowed no let-up. "We will not stop fighting until we capture all the army bases and the honourable members of the armed forces join us," he told Al Jazeera.

Created in 2013, the RSF emerged from the Janjaweed militia that then president Omar al-Bashir unleashed against non-Arab ethnic minorities in the western Darfur region a decade earlier, drawing accusations of war crimes.

A plan to integrate the RSF into the regular army is one of the main points of contention, analysts have said.

Haggling between the two men has twice forced postponement of the signing of an agreement with civilian factions setting out a roadmap for restoring the democratic transition disrupted by the 2021 coup.

Witnesses also reported clashes around the state media building in Khartoum's sister city Omdurman.

Outside the capital, witness Eissa Adam said explosions and gunfire had been heard across the North Darfur state capital of El Fasher, where civilians were hunkered down inside their homes.

Witnesses in the South Darfur state capital Nyala also reported clashes.

The two sides traded blame for starting the fighting.

The RSF said they were "surprised Saturday with a large force from the army entering camps", reporting a "sweeping attack with all kinds of heavy and light weapons".

Army spokesman Brigadier General Nabil Abdallah said the paramilitaries launched the fighting, attacking "several army camps in Khartoum and elsewhere around Sudan".

"Clashes are ongoing and the army is carrying out its duty to safeguard the country", he added.

Burhan, in a statement to Al Jazeera, said he "was surprised by Rapid Support Forces attacking his home at 9:00 am", without giving details.

- 'Slipping into abyss' -

The military's civilian interlocutors called on both sides "to immediately cease hostilities and spare the country slipping into the abyss of total collapse."

Their plea was echoed by US ambassador John Godfrey, who tweeted that he "woke up to the deeply disturbing sounds of gunfire and fighting" and was "currently sheltering in place with the embassy team, as Sudanese throughout Khartoum and elsewhere are doing".

The head of the United Nations mission in Sudan, Volker Perthes, called for an "immediate" ceasefire, to "spare the country from further violence".

Western governments had been warning of the dangers of all-out fighting between the rival security forces since the army issued its warning to the paramilitaries on Thursday.

Daglo has said the 2021 coup was a "mistake" that failed to bring about change in Sudan and reinvigorated remnants of Bashir's regime ousted by the army in 2019 following month of mass protests.

Burhan, a career soldier from northern Sudan who rose the ranks under Bashir's three-decade rule, maintained that the coup was "necessary" to bring more groups into the political process.

© Agence France-Presse