The United Nations on Friday sounded the alarm over an upsurge in vicious communal violence in conflict-hit South Sudan, after dozens were killed in an attack on civilians sheltering in a UN base.
UN officials said "dozens" of people were killed and scores more wounded on Thursday by gunmen posing as peaceful protestors who stormed a UN base in the war-ravaged town of Bor, one of several sites where thousands of people are sheltering from ethnic violence.
The US ambassador to the world body, Samantha Power, said at least 20 were confirmed dead, while the top UN aid official in South Sudan, Toby Lanzer, said dozens were dead. Local officials, speaking on condition of anonymity, said as many as 50 people were dead.
"Humanitarian partners are particularly outraged by deliberate and targeted killings of civilians in hospitals, churches, UN peacekeeping bases and other places where people's rights should be sacrosanct," the UN's aid agency UNOCHA said in a statement.
"People came into UNMISS bases in fear of their lives. People are already afraid and will now be even more so," UNOCHA's Amanda Weyler told AFP.
According to UN officials, the attackers used rocket-propelled grenades to breach the compound then fired on those sheltering inside.
Most of the 5,000 people hiding in the UN base in Bor are thought to be ethnic Nuer, the same tribe of South Sudan rebel leader Riek Machar.
Machar, a former vice president, has been fighting against President Salva Kir, an ethnic Dinka, for the past four months.
Initial reports indicate the attack was carried out by armed Dinka youth furious over the fall to rebels this week of the town of Bentiu, an oil-producing hub further to the north.
The conflict in South Sudan has left thousands dead and forced around a million people to flee their homes since fighting broke out on December 15 in the capital Juba.
The unrest quickly spread to other states in the oil-rich nation, which only won independence from Sudan in 2011.
The fighting has been marked by reports and allegations of atrocities by both sides, with ethnic massacres, child soldier recruitment and patients raped and murdered in hospitals by attacking forces.
The UN and humanitarian aid agencies have also been left facing a mammoth crisis, including feeding and sheltering 67,000 civilians across the country who are sheltering inside UN bases and warning that more than one million people are at risk of famine.
"Worse is yet to come," said Jonathan Veitch, the head in South Sudan of UN children's agency UNICEF in a statement.
Power urged countries that have committed additional forces to UNMISS to speed up their deployment, and said the United States will work with its allies to determine who was responsible for the "horrific attack" in Bor and bring its perpetrators to justice.
The US was instrumental in helping South Sudan gain independence, but has so far proved powerless or unwilling to firmly intervene. The US ambassador to the UN, however, signalled that patience was running out with the warring factions.
"This latest outrage against the people of South Sudan is an affront to the international community and violates fundamental principles of civilian protection," Power said, adding that UNMISS sites should be considered "inviolable".
A spokesman for UN chief Ban Ki-moon said the attack on the UN base was a "serious escalation" in the crisis.
"The Secretary-General reminds all parties that any attack on United Nations Peacekeepers is unacceptable and constitutes a war crime," he warned.
Earlier this week, rebel leader Machar told AFP he had set his sights on oil fields in the north and the capital Juba, and after the fall of Bentiu, government officials have reported more heavy fighting across the oil-rich Unity State.