More residents of South Sudan’s capital were packing up belongings and fleeing for the border with Uganda on Sunday after several hours of fierce clashes during the night.

More residents of South Sudan's capital were packing up belongings and fleeing for the border with Uganda on Sunday after several hours of fierce clashes during the night.

Juba was rocked by heavy gunfire late on Saturday, with exchanges of automatic and heavy weapons fire heard coming from a district in the south of the city before calm returned in the early hours of the morning.

There was speculation that another army unit had defected to the rebels, although army spokesman Philip Aguer told media outlets that the government was "investigating exactly what happened" during the night.

A police spokesman said the fighting may have been caused by "criminals trying to scare people so they can go into houses and steal".

After a terrifying night sheltering in their homes, more residents could be seen trying to get transport south to Uganda, adding to the nearly 200,000 people who have already been displaced by the three-week-old conflict.

The conflict erupted on December 15, pitting army units loyal to President Salva Kiir against a loose alliance of forces and army commanders nominally headed by his rival, former vice president Riek Machar.

Kiir has accused Machar of starting the unrest by attempting a coup, although Machar denies this and in turn accuses the president of conducting a violent purge of his rivals.

The fresh fighting also came as representatives from both sides were set to sit down in earnest for face-to-face talks in the Ethiopian capital Addis Ababa aimed at ending the conflict.

The conflict has already left thousands dead, according to UN officials, with both sides alleged to have committed atrocities.