The UN has accused Ivory Coast state media - controlled by strongman Laurent Gbagbo - of inciting hatred against foreign peacekeepers.
UN peacekeeping chief Alain Le Roy said state TV channel RTI was pumping out lies, and blamed it for a machete attack on UN personnel on Tuesday.
Mr Gbagbo has so far resisted UN calls to step down as president and make way for his rival Alassane Ouattara.
Regional leaders are holdings talks aimed at breaking the impasse.
The presidents of Benin, Sierra Leone and Cape Verde, sent by regional bloc Ecowas, came away on Wednesday without a deal.
Ecowas, which had threatened in a statement to send in troops to force Mr Gbagbo to step down, said the three men would return to the country on 3 January for more talks.
'Appeals to hatred'
An election last month resulted in both Mr Gbagbo and Mr Outtara being declared the winner, and each being sworn in as president.
On Wednesday, the UN solidified its support for Mr Outtara by formally welcoming his choice as the country's ambassador to the UN.
And in a news conference, Mr Le Roy launched an unprecedented attack on state TV.
"The declarations I hear on the RTI are concerning us and shocking us, because they clearly instigate the population to turn against ONUCI [UN mission in Ivory Coast]," he said.
He said an incident where a peacekeeper was wounded with a machete when his patrol was encircled by angry crowds was a "direct consequence of all the appeals to hatred, lies and anti-ONUCI propaganda".
Despite international support, Mr Outtara and his Prime Minister Guillaume Soro remain holed up in a hotel in the main city of Abidjan, protected by UN forces.
Supporters of Mr Gbagbo, known as "young patriots", have threatened to storm the hotel.
Young patriots leader Charles Ble Goude, who is also Mr Gbagbo's youth minister, also warned Ecowas not to send troops.
"They should prepare themselves very well because we are thinking about totally liberating our country, and soon I will launch the final assault," he said.
Mr Ble Goude is renowned for his fiery rhetoric and has reportedly made such threats before without carrying them out.
But analysts have warned that inflammatory rhetoric could help push the nation back into civil war, seven years after a previous conflict resulted in it being divided between a rebel-run north and government-controlled south.
The UN has some 9,500 peacekeepers in the country.
Mr Gbagbo has told them to leave, accusing them of interfering in Ivorian affairs.
But the UN has refused to do so. It says at least 173 people have died in violence and scores of others have been tortured since the 28 November elections.
Almost 20,000 people - mostly women and children - have fled Ivory Coast for neighbouring Liberia, fearing further unrest.