Both Kiir and Machar have ordered a ceasefire.
The UN Secretary-General called on the Security Council to implement an immediate arms embargo on the country and called for additional sanctions against South Sudanese leaders blocking implementation of the peace agreement signed a year ago. The war was fought broadly between South Sudan's biggest ethnic groups - the Dinka, led by Mr Kiir, and the Nuer, under Mr Machar.
It seems a disagreement at a checkpoint between rival soldiers led to a shootout on Thursday night in which five soldiers died.
A witness told Reuters that two helicopter gunships had flown over the city and opened fire in the direction of Mr Machar's headquarters.
On Friday evening, gunfire erupted outside the presidential palace where President Salva Kiir and Vice-President Riek Machar were meeting.
The United Nations Secretary General, Ban Ki-moon, has stated that South Sudanese leaders have failed their people in the wake of renewed fighting that is threatening to derail the August 2015 peace deal.
South Sudan's president on Monday ordered the army to cease hostilities and protect civilians, effective immediately. About half of South Sudan's population of 11 million people are threatened with starvation, inflation is at 300%, and the country is effectively bankrupt.
Clashes between troops loyal to the two men threatened a recent peace deal.
A hospital operated by the International Medical Corps was hit by shelling but no one was injured and the patients had to be relocated, the organization said.
It warned that attacks on civilians and the United Nations could amount to war crimes.
The 15-member Council on Monday condemned the deadly violence in South Sudan and urged calm in the wake fresh clashes in Juba between soldiers of the Sudan People's Liberation Army (SPLA) and the SPLA in Opposition.
What can the worldwide community do?
In the past, however, China and Russian Federation have stood in the way of the Security Council's approval of an arms embargo on South Sudan.
She assured actor Akshay Kumar who tweeted her The government has in an advisory issued yesterday against traveling to South Sudan till the situation improves. "We condemn this outbreak of violence in the strongest terms possible and call for the immediate restoration of peace in the country", said Deputy President Ramaphosa.