Juba (AFP) - South Sudan's vice president and former rebel leader Riek Machar has no plans for an immediate return to Juba, his supporters said Friday, accusing his rival President Salva Kiir of trying to oust or even kill him.

Machar has not been seen in public since he left the capital after days of intense fighting this month between rival troops that left over 300 people dead and threatened to torpedo an already shaky 2015 peace deal.

Kiir had appealed on Thursday for Machar to return to Juba and work together towards rebuilding peace, pledging to guarantee his safety.

"There is no point to come back to be assassinated," Machar's spokesman Goi Jooyul Yol told AFP, speaking from the Ethiopian capital Addis Ababa.

"Dr Machar is still being hunted around Juba," he said, adding that "we don't trust" Kiir's security pledge.

"He has killed the peace agreement. The only way forward is a neutral force," the spokesman insisted.

- 'Devastating blow' -

Kiir has rejected a proposal by the African Union to deploy a robust protection force in South Sudan and is also against beefing up the mandate of the UN peacekeeping mission UNMISS.

But Machar's movement, known as the SPLM/A (IO), is in favour of a independent force.

"This is because South Sudan has no national armed forces, no national security agency. The existing armies are all partisan and ethnic in character," it said in a statement.

The SPLM/A (IO) statement reaffirmed the group's support for Machar's leadership and denouncing what it said were government efforts to replace him with Taban Deng Gai, who was the chief negotiator for the former rebels during the peace talks.

Any attempt to change Machar's role as chairman and commander in chief of the SPLM/A (IO) "is totally rejected," the statement said.

"It will deal a devastating blow" to the government of national unity and the August 2015 peace accord which aimed to end a near two-year civil war in the world's youngest nation.

The statement called on the government "to cease with immediate effect their ongoing military attempts to hunt down and kill (Machar) in their vain hope of installing Taban Deng Gai as the first vice president".

"Salava Kiir can appoint him (Taban Deng Gai) first VP. That up to him. But he cannot (make him) chairman of the SPLA/IO," said Goi Jooyul Yol.

Juba was rocked by days of heavy fighting in early July between government forces and fighters loyal to Machar which erupted as he was meeting Kiir in the presidential palace.

More than 300 people were killed and tens of thousands of people fled, escalating fears of a return to the brutal civil war that erupted just over two years after independence in 2011.

The latest violence in the capital echoed the fighting that first triggered the civil war in December 2013, when Kiir accused Machar of plotting a coup.