A Russian-built cargo plane has crashed in South Sudan shortly after take-off from Juba International Airport, killing dozens of people.

The exact death toll remains unclear after the Antonov-12B plane crashed around a mile from the airport, leaving debris along the banks of the River Nile.

One witness told Reuters there were 41 bodies at the crash site. Another witness said 32 people had died.

Presidential spokesman Ateny Wek Ateny said the aircraft was carrying 18 people, including six crew members.

He added that only three of those aboard the plane survived, one of them a child and all South Sudanese nationals.

There were five Armenians and one Russian national among the crew.

"This is the number given to us by the (control) tower," Mr Ateny said.

An unknown number of people were also killed on the ground when the plane came down near a group of fishermen.

Officials say the plane belonged to the freight and logistics firm Allied Services Ltd.

It was travelling to the Paloch oil fields in Upper Nile state at the time of the crash.

Stephen Warikozi, the chief executive of the Civil Aviation Authority at Juba International Airport, said: "We have rushed to the site of crash which is located near the airport, southeast of Juba International Airport (across) the river".

"We have secured the site of crash and also we are in the stage of recovering bodies and black box. We are still now recovering the dead bodies and we cannot give you the exact number".