New clashes have broken out in Yambio, the capital of South Sudan's Western Equatoria state.

The clashes began around 5 o'clock Thusrday morning, according to a source. Gunfire has continued on and off until now, sources said. Casualties were reported though there are no concrete figures yet.

The market is reportedly empty with civilians seeking shelter in their homes or near the United Nations base in the town, a source said. That source said some people are afraid to reach the UN base because shooting has been heard in the area of the base.

The fighting took place mainly on the southern side of the town near the prison, according to sources. That area is near a frontline between the government-controlled Yambio town and Gangura Payam which is held by the South Sudan National Liberation Movement.

A source within the SSNLM accused SPLA soldiers on military vehicles of crossing the frontline near the Yambio power station early in the morning and attacking their positions. The source denied that SSNLM forces crossed into Yambio town, saying he did not know who was involved in shooting inside the town itself.

The SSNLM is a militia led by ex-SPLA commanders from Western Equatoria. The SSNLM signed a preliminary peace agreement with the government in November, but the deal has yet to be finalized.

A spokesperson for the UN Mission in South Sudan told Radio Tamazuj that fighting began at approximately 10:40 am in Yambio town, reportedly between the SPLA and the SSNLM. The spokesperson said at least 2000 people have taken refuge at an NGO compound next to the UN base in Yambio.

"Currently the number of casualties are unknown," the spokesperson said. "UNMISS carried out a number of patrols into the town today and reported the town is deserted with all businesses closed."

This story has been updated at 16:11, 21/1/2016 with information from a source within the SSNLM, and at 18:07, 21/1/2016 with information from UNMISS.