Sudan's president Omar al-Bashir has called South Sudanese president Salva Kiir and first vice president Riek Machar by phone and urged them both to show restraint as new fighting occurred in Juba, Sudan News Agency (SUNA) reports.

According to SUNA, al-Bashir told the two men to stick to self-restraint and to elevate the interest of South Sudan people for the sake of guaranteeing stability at the region.

"He stressed the necessity of avoiding bloodshed and dragging the area into tribal and political disputes that will hinder the peace and development process in South Sudan State," the state news service said.

Hundreds have been killed in South Sudan's capital Juba since Thursday night when skirmishes began escalating to large battles between Kiir and Machar's forces.