UN Security Council members are considering sanctions on South Sudan's warring parties, envoys said, after UN peacekeeping chief Herve Ladsous demanded "serious consequences" be imposed to force an end to the violence.

Ladsous and UN Assistant Secretary-General for human rights Ivan Simonovic briefed the 15-member council on a recent escalation in attacks on civilians, including an ethnic massacre in the oil town of Bentiu and the killing of dozens of people who had sought refuge inside a UN peacekeeping base in Bor.

"Unless there are serious consequences for the parties to cease the violence and engage in meaningful talks ... the toll on innocent civilians will continue to rise," Ladsous told reporters on Wednesday after the closed-door council meeting.

Nigerian UN Ambassador Joy Ogwu, president of the council for April, said there was a lot of support among council members for pursuing sanctions on South Sudan.

"I think we are ready to go down the road of sanctions," French UN Ambassador Gerard Araud told reporters.

US ambassador to UN Samantha Power posted on Twitter after the briefing "for the sake of the people of South Sudan, international community must sanction political spoilers and those who target civilians."

China, the biggest investor in South Sudan's oil industry, said it would "conscientiously participate" in UN Security Council discussions and was in favor of promoting talks between all sides in the country.

"China has energy companies operating in South Sudan. We hope to see peace and stability in the country. We also ask the government of South Sudan to protect the legitimate and lawful interests of local Chinese companies and the safety of Chinese personnel there," Chinese foreign ministry spokesman Qin Gang said on a press briefing.

More than 1 million people have fled their homes since fighting erupted.