Kyrgyzstan must set up a humanitarian corridor to help people affected by deadly fighting between ethnic Kyrgyz and Uzbeks, a top UN official says.
Lynn Pascoe said he also wanted to get help to Uzbekistan to make sure it could deal with the influx of refugees.
Tens of thousands of ethnic Uzbeks have fled their homes in Kyrgyzstan and headed for Uzbekistan.
The violence began in the southern cities of Osh and Jalalabad on Thursday and has left at least 170 dead.
The BBC's Rayhan Demytrie in Osh says there were more reports of fighting overnight, and there was no indication the violence would end.
Kyrgyzstan's interim government, which came to power after violent protests overthrew the previous administration, has been quick to blame supporters of ousted President Kurmanbek Bakiyev.
Mr Bakiyev, who now lives in exile in Belarus, still has widespread support in the south, but he has denied whipping up tensions.
Kyrgyzstan's interim leader Roza Otunbayeva said on Tuesday that there was no need for a peacekeeping force in the country, and that a constitutional referendum would go ahead on 27 June.
Bodies in the streets
Mr Pascoe, a UN undersecretary-general, briefed the Security Council on the situation, and told reporters after that he had stressed the need to "get something in there right away".
"It's also a great concern of ours about the refugees - whether they can get across the border," he said.
"What we are trying to do is get [Uzbekistan] enough assistance there that they can feel comfortable with additional refugees coming through."
Eyewitnesses in Osh and Jalalabad have reported seeing whole rows of houses burnt down, and bodies lying in the streets.
Earlier, UN Human Rights Commissioner Navi Pillay said there was evidence of indiscriminate killings - including of children - and of rapes.
A spokesman for Ms Pillay, Rupert Colville, told the BBC that some of the killings were apparently indiscriminate.
"We're also getting reports that it's not accidental, that it's been orchestrated, targeted, planned... (we) can't prove that at this point but that seems to be the indication."
Uzbek refugees say that armoured vehicles in Osh drove through streets in Uzbek neighbourhoods, shooting at civilians and clearing the way for gangs following behind.
Pascale Meige Wagner, from the International Committee for the Red Cross, said the death toll was an underestimate. "We hear about bodies not being recovered in Osh and Jalalabad," she said.
"We do believe that once the situation is a bit quieter in those two towns we'll have a better idea of the dimension of this crisis."
Ethnic Uzbeks make up about 15% of Kyrgyzstan's 5.5 million people.
Central Asia's patchwork of ethnic groups competing for wealth and resources in countries controlled by their rivals has been described by UN officials as a "tinder-box".
They fear that the violence - the worst the region has seen since Soviet times 20 years ago - needs to be stopped quickly, or it could soon spread to other parts of the region.