Fighting in Sudan raged for a second day Sunday after battles between Sudanese paramilitaries and the regular army killed at least 56 civilians and wounded hundreds more people, sparking international alarm.

Deafening explosions and intense gunfire shook buildings in the capital Khartoum's northern and southern suburbs as tanks rumbled on the streets and fighter jets roared overhead, witnesses said.

Violence erupted early Saturday morning after weeks of deepening tensions between army chief Abdel Fattah al-Burhan and his deputy, Mohamed Hamdan Daglo, commander of the heavily-armed paramilitary Rapid Support Forces (RSF), with each accusing the other of starting the fight.

Both sides claim they control key sites.

Daglo's RSF say they have seized the presidential place, Khartoum airport and other strategic sites, but the army insists they are in charge, with the air force late Saturday urging people to stay indoors as it continued air strikes targeting RSF bases.

Footage obtained by AFP showed heavy smoke billowing from a building near the army headquarters in central Khartoum.