A UN peacekeeping base in South Sudan's Jonglei state was attacked on Thursday and the United Nations has received reports that some people have been killed, deputy UN secretary-general Jan Eliasson said.

"Our base in Akobo, Jonglei State, was attacked and we have reports that lives are lost. We don't have the details of that yet," Eliasson told reporters.

UN spokesman Farhan Haq also spoke about the Akobo attack.

"The situation in Jonglei has deteriorated," he said. "In Akobo, earlier today, where civilians have gathered, including 32 as of last night, Lou Nuer youth have reportedly forced an entry into the UNMISS Temporary Operating Base to reach to those civilians."