UNITED NATIONS (AP) — The new U.N. envoy in South Sudan expressed shock Wednesday at the complete disregard for human life in the world's newest nation and urged international pressure on President Salva Kiir and former Vice President Riek Machar to end their power struggle and silence their guns.

Ellen Margrethe Loj told the U.N. Security Council that a comprehensive peace agreement must be concluded without further delay so South Sudan can return to the path of peace.

Fighting broke out in the world's newest nation in December after Kiir, an ethnic Dinka, accused Machar, an ethnic Nuer, of trying to oust him in a coup. Their political dispute sparked months of ethnic attacks and fighting between government troops and rebels, despite several cease-fires.

The toll has been huge, with thousands killed and more than 1.8 million people forced to flee their homes — 1.35 million who remain in the country including nearly 100,000 who sought refuge in U.N. peacekeeping camps and over 450,000 who crossed into neighboring countries.

"The humanitarian situation across the country remains dire," Loj said, with around four million people, close to a third of the population, facing "serious food insecurity."

Loj, who heads the nearly 11,400-strong U.N. peacekeeping mission in the country, told a group of reporters later that she was shocked at the disregard for human life because of the high number of civilian casualties.

"There's a lot of weapons around in South Sudan and they use them unfortunately against one another if you have a disagreement," she said.

The regional body known as IGAD, which is peace mediating talks between Kiir and Machar in neighboring Ethiopia, announced in late September that South Sudan's warring factions have to establish a federal system of government in the country. It said the structure and functions of a transitional government of national unity have been "mostly agreed on."

Loj, who is not involved in the talks, said that while the Security Council was meeting on Wednesday the prime minister of Ethiopia, the president of Kenya and the foreign minister of Uganda were in South Sudan's capital, Juba, for talks with Kiir. They are likely focusing on a transitional government "and whether there will be a president and a prime minister and who they would be and (a) timeline," she said.

Loj expressed hope that Kiir and Machar will sign an agreement.

"At least if we can get the guns to be silent there is a bigger room, so to speak, to try to do our work in terms of protecting civilians, monitoring human rights, getting humanitarian assistance," she said.

But Loj stressed that because it has turned into an ethnic conflict, "even if the two political leaders sign an agreement, a lot of reconciliation work will need to take place on the ground to solve the problem."

The U.N. special representative on sexual violence in conflict, Zainab Hawa Bangura, told the council that the overall conditions she saw in her weeklong visit to South Sudan this month were "among the worst I have ever experienced."

"My visit bears out reports that sexual violence in South Sudan is widespread, including acts of rape, gang rape, abductions, forced marriage and sexual slavery, and mutilation of sexual organs," Bangura said.