The United Nations Mission in South Sudan (UNMISS) on Friday also confirmed that the fighting was going on towards Juba.
Col. Mike Chadrick of UNMISS in Bor told the BBC he independently verified that two armed groups were fighting about 40 miles away on Juba-Bor road.
The situation was calm in Bor town, he said, which remains under the control of pro-Machar forces.
A rebel commander, Bridagier General Khor Chol, who took part in the Friday engagement, also said the government soldiers were retreating back to Juba and will not be able to stop them from advancing in to Juba.
"We are currently pursuing pro-Salva Kiir soldiers. We are surely matching and will enter Juba soon," he said.
He added the government was not telling the truth to the citizens about "what is actually taking place on the ground in the battle fields", adding that government spokespersons employed "propaganda of lies with the aim to deceive the public."
He described Aguer's claim of trying to attack Bentiu in Unity state as a "mere propaganda" and a desperate attempt to raise the morale of the "demoralised" government troops.
Khor cautioned the residents of Juba to stay indoors or seek refuge with UNMISS as the rebels would storm the capital "any time soon."
CEASEFIRE TALKS ON
Meanwhile, the two parties are set to start a face-to-face negotiation of a ceasefire on Saturday in the Ethiopian capital Addis Ababa.
Machar's group has demanded the release of their colleagues detained in Juba in order to agree on a ceasefire.
They also want them flown to Addis Ababa to take part in the negotiations.
The rebel further want the government to denounce that there was no alleged coup attempt as one of the pre-conditions for a ceasefire.