France and the US have called for the United Nations Security Council to consider sanctions against South Sudan over spiralling violence in the country's civil war.
US ambassador Samantha Power relayed Washington's position in a closed-door meeting of the 15-member Council.
Later, on Twitter, she wrote: "For the sake of the people of #SouthSudan, international community must sanction political spoilers and those who target civilians." She also said that the latest atrocities brought the country to a "turning point".
France's Gerard Araud told reporters before the session on Wednesday that it was time to think about sanctions against those responsible.
"I think we should consider sanctions because it is horrendous," he said.
In December, the Security Council agreed to almost double the size of the UN peacekeeping force in the country, but few of the extra troops have actually arrived.
"Maybe we have to face the fact that we can't cooperate with this government any more ... We need some soul-searching about what the UN should do in South Sudan," said Araud.
The Security Council stopped short of announcing any immediate decision after breaking up its talks, the AFP news agency reported.
Current Security Council president Nigeria said members were united in their determination that an attack last week on a UN base in the government-controlled town of Bor should not happen again.
"Most of us suggested using the principle of deterrence to send a message unequivocally to the parties responsible for this impunity," said Nigerian ambassador Joy Ogwu.
"They can violate the sanctity of the UN institutions and kill people inside those institutions? It's intolerable. It should not happen," she added, without mentioning the word "sanctions."
Escalation in conflict
UN peacekeeping chief Herve Ladsous demanded an immediate end to the violence and warned that with the changing season, a "humanitarian catastrophe" would become more certain.
The UN Security Council has said last Thursday's attack on a UN base which killed at least 58 people may constitute a war crime.
The attack on the UN compound and the killing of unarmed civilians "denotes a serious escalation in the conflict and it does create an extremely dangerous precedent," Ladsous said.
"Unless there are serious consequences for the parties to cease the violence and engage in meaningful talks... then the toll on innocent civilians will continue to rise," he said.
He accused the South Sudan government of impeding UN officials' freedom of movement and preventing them from doing their job.
On Tuesday, the White House expressed horror at the "abomination" of the violence in South Sudan, where rebels have been accused of massacring hundreds of civilians.
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Rebels seized the oil hub of Bentiu last week, unleashing two days of ethnic slaughter as they hunted down civilians sheltering in mosques, churches and a hospital, butchering dozens on the roadside, according to the UN.
Images released by the United Nations show piles of bloated, decomposing bodies, a repeat of mass killings seen in other areas of the country during the past four months.
The UN said the killings continued for almost two days after the rebels proclaimed victory in Bentiu, and that the rebels had used radio broadcasts to stir violent ethnic sentiment.