Southern Sudanese rioted Monday amid rumors that vice president and former southern rebel leader John Garang's death in a helicopter crash was not accidental.

The skies over Khartoum filled with billowing black smoke Monday afternoon, as angry mobs set cars on fire and exploded home-made bombs outside the palace of Sudanese President Omar al-Bashir and elsewhere in the city. Gunfire could also be heard throughout Khartoum as Sudanese police and military arrested demonstrators.

The violence followed the death of John Garang in a helicopter crash Sunday. The government in Khartoum called the crash a tragic accident, but that didn't stop rumors from spreading throughout the capital that the former rebel leader was murdered.

Rashid Khider, secretary-general of the Sudanese External Information Council told VOA that rioting was unwarranted. "You cannot make demonstrations when this is a time of mourning," he said. "Demonstrations against who? Against fate, the will of God?"

From the rooftops of Khartoum it was possible to see thick, black smoke and several flashes of fire emanating from the direction of the presidential palace. Moments later, civilians were told to leave the rooftop and soldiers took their places.

Armed police and military blocked the streets of central Khartoum, and pedestrians were diverted from the center of town, where much of the violence occurred.

Dozens of men wearing neither army nor police uniforms stood with machine guns in the roads, stopping cars and questioning drivers.

From an abandoned building, this reporter witnessed a suspected instigator of the violence being beaten and kicked to the ground by Sudanese soldiers and men in civilian clothing. The man was kicked while lying on the ground and then dragged away by security forces.

As the streets calmed, shopkeepers began to sweep up broken glass from shattered store windows. A burned van blocked a main street. Groups of schoolchildren scurried nervously home.

In a press statement issued Monday afternoon, the Sudanese government urged all citizens to stay calm "until the country passes this difficult test."

Mr. Garang was a hero among many Southern Sudanese. His rebel Sudan People's Liberation Army waged a 21-year war against the northern government. He became vice president less than a month ago following the signing of a peace agreement last January.

Many Sudanese appeared to be in shock and would not accept the reports that Mr. Garang had died. Women wept in the streets and men shook their heads in disbelief. William, a southern Sudanese who declined to give his last name, was full of emotion. "He's alive," he insisted. "Nobody can kill him. I don't believe it. I don't believe it. I don't believe it. I don't believe it. If he's dead I'm going to be dead too, right now. If he's dead on the street, I will be dead."

By the day's end, an uneasy calm settled over central Khartoum. The street were quiet except for the sounds of shopkeepers sweeping up broken glass and police sirens blaring in a distance.