At least 169 people were killed after insurgents raided a village in a remote area of South Sudan, a local official said Monday. It's the latest bout of sporadic violence that has left the country teetering on the verge of full-blown civil war.

The victims, including 90 civilians, were attacked on Sunday in Abiemnom county, said James Monyluak, information minister for the administrative area of Ruweng. He said women and children were among the dead, in addition to dozens of combatants.

The U.N. Mission in South Sudan, known as UNMISS, said in a statement that 1,000 people sought shelter at its base after the attack.

"Such violence places civilians at grave risk and must stop immediately," Anita Kiki Gbeho, a UNMISS official, said in a statement. "I urge all involved to cease hostilities without delay and engage in constructive dialogue to address their grievances."

"Our peacekeepers will continue to do everything within their capabilities to protect civilians seeking refuge at our base," she added.

The UNMISS statement cited 23 wounded in the attack in Ruweng, as well as concern over "reports indicating that dozens of civilians and some local officials have lost their lives."

On Monday, UNMISS said its peacekeepers were patrolling the area all night long, "deterring crime and protecting civilians, demonstrating their commitment to the people of South Sudan."

"When I joined the army to serve my country, I never realized that I would end up providing security for civilians in another country," Lance Corporal Amenuvor Mabel of the Ghana Battalion, who led the night convoy, said in a statement. "It makes me feel good that we are serving people and making them feel safe."

The killings are part of an escalating wave of violence gripping South Sudan as government forces loyal to President Salva Kiir battle armed men who are believed to be loyal to opposition leader Riek Machar.

Stephano Wieu De Mialek, the chief administrator of Ruweng Administrative Area, said on Sunday that the assault was conducted by elements linked to the White Army militia alongside forces affiliated with Machar's Sudan People's Liberation Movement-in-Opposition. Wieu described the attack as a coordinated and organized assault, calling it an act of rebellion.

In a statement, Machar's group denied responsibility for the attack and asserted that it "has no military presence in the area concerned."

Machar was Kiir's deputy until September, when he was removed after he faced criminal charges. He is under house arrest in Juba, the South Sudan capital, as his trial progresses.

The U.S. is urging talks between Kiir and Machar.

Ongoing violence threatens a fragile peace reached in 2018 after a five-year civil war. After that agreement, Machar was named South Sudan's first vice president in a government of national unity. A U.N. inquiry has found that South Sudan's leaders are "systematically dismantling" that agreement.

Machar's supporters say the charges against him for alleged subversion are politically motivated. His removal from office coincided with a sharp increase in violence.

The conflict escalated in December when opposition forces seized government outposts in the county of Jonglei, an opposition stronghold and a flashpoint in renewed fighting that the U.N. estimates has displaced 280,000 people.

In December, UNICEF executive director Catherine Russell told CBS News that what is happening in Sudan is the "largest humanitarian crisis" the organization is seeing.

"The challenges are absolutely staggering," she told CBS News' Margaret Brennan.

Aid groups have warned that access restrictions to opposition-held parts of the state are endangering civilian lives.

The government has conducted a counteroffensive since January with aerial bombardments and ground assaults, despite an official commitment to the peace agreement.

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