The United Nations has condemned the "targeted killings" of civilians in South Sudan based on ethnicity or nationality. Hundreds of people have been killed since rebels seized a key oil town last week.
The UN mission in South Sudan issued a report on Monday outlining the findings of human rights investigators on the ground in Bentiu, the capital of oil-producing Unity State.
It said more than 200 people were found dead and hundreds more injured in the city's Kali-Ballee mosque last week.
Detailing the atrocity, it said rebels "separated individuals of certain nationalities and ethnic groups and escorted them to safety, while the others were killed."
The report said several men, women and children from the Nuer ethnic group were also found dead inside Bentiu Hospital. They were reportedly killed for hiding and declining to join other Nuers who had come out to cheer for the rebels as they seized the town.
Similar massacres also took place at a Catholic church and an abandoned UN World Food Programme compound, where people were sheltering.
Thousands of people have been killed across South Sudan since December when former Vice President Riek Machar reportedly attempted to seize control from President Salva Kiir.
The two hail from rival ethnic groups, adding a dangerous sectarian element to fighting. Machar's forces are largely Nuer, while troops fighting on the side of Kiir are Dinka.
A ceasefire was signed in January in a bid to quell hostilities, although that has largely been ignored and rebel fighters launched a fresh offensive last month to capture key oil fields.
Incitement to rape
Rebels ousted government troops from Bentiu on Tuesday and according to the UN report then spent two days hunting down those it believed were opposed to them.
"They (the rebels) searched a number of places where hundreds of South Sudanese and foreign civilians had taken refuge, and killed hundreds of the civilians after determining their ethnicity or nationality," the UN said.
Toby Lanzer, the top UN aid official in the country, told RFI radio on Monday what he had witnessed was "beyond description", describing "a never-ending stream of spots where people have been executed, very deliberately targeted."
There were also reports that rebels had taken control of Radio Bentiu and were using it to broadcast hate speech.
The UN said rebels told listeners to "force rival groups from the town declaring that certain ethnic groups should not stay in Bentiu, and even calling on men from one community to commit vengeful sexual violence against women from another community."
The capture of Bentiu came two days before gunmenstormed a UN compound killing at least 58 people
who were sheltering there.
The UN Security Council has said that the attack could "constitute a war crime."
ccp/kms (AFP, AP, dpa)