At least 166 civilians have been killed and 237 others injured in the last four months in clashes in South Sudan's Upper Nile State, United Nations High Commissioner for Human Rights Volker Turk said on Wednesday.

"These killings, along with reports of gender-based violence, abductions, destruction of property and looting, are severe human rights violations and abuses and must stop," Turk said in a statement.

South Sudan's Upper Nile State has experienced violence since August, which also displaced thousands of civilians, mostly children and women, according to the UN.

Turk urged the government to conduct a prompt, thorough and impartial investigation into the violence and bring all those responsible to account in accordance with international law.

He also called on community leaders and elders to use their influence over the groups involved in the violence to end the bloodshed.

"I urge those perpetuating this senseless violence to lay down their weapons and to engage in dialogue to address any grievances peacefully," Turk said.

He said civilians have been subjected to forced displacement by the threat of violence, and that the increased insecurity has slowed the delivery of urgent, life-saving humanitarian support.

Turk expressed serious concerns that the violence risks spreading beyond the region, urging the authorities to act swiftly to de-escalate the tension and provide protection to the affected communities.