The International Committee of the Red Cross has described the humanitarian situation in southern Kyrgyzstan as an "immense crisis".
The warning by Severine Chappaz, deputy head of the ICRC, came as humanitarian agencies began delivering medical aid, food and shelter to people who have fled the ethnic unrest in Kyrgyzstan.
The official figure of 191 killed during the deadly clashes, which broke out on Friday in the Central Asian nation, is expected to be as much as several hundred.
The Kyrgyz army has tried to regain control of Osh, the epicentre of the violence that drove much of the Uzbek population from the country's poor, rural south.
Al Jazeera's Robin Forestier-Walker, reporting from Osh on Thursday, said that the situation in thte city was still very tense.
"The ethnic Uzbek people are terrified of anyone in uniform. Therefore if there is any aid, it is difficult to get it to them," he said.
Russia has said it will not send peacekeepers to Kyrgyzstan.
However, the Collective Security Treaty Organisation (CSTO), a Russian-led body, has said it may send "security specialists" to Kyrgyzstan.
"We are looking at the question of sending specialists to the republic who know how to plan and prepare operations to prevent mass disorders," Nikolai Bordyuzha, the CSTO secretary-general, said on Thursday.
He did not provide more information about what the "specialists" would do.
Anna Neistat, spokeswoman for the emergency unit of Human Rights Watch, said that there was no ethnic fighting going on anymore, "but there is very little security despite what the authorities claim.
"Tensions in neighbourhoods are rising because people are without food and water".
She was in Osh to investigate allegations of human-right abuses and said that most of those killed were men.
Responding to claims by UN agencies of "an alarming rate" of rapes and killings against children and civilians, Neistat said: "There definitely have been cases of rape, but there is not enough information yet to confirm the reports."
The UN said that 300,000 people have been displaced within the country and an additional 100,000 have fled to neighbouring Uzbekistan.
Two aircraft carrying hundreds of tents supplied by the UNHCR arrived in Uzbekistan on Wednesday and four more were due to arrive by the end of the week.
Another aircraft carrying relief supplies from the ICRC including blankets, tarpaulins, cooking utensils and soap has arrived in southern Kyrgyzstan.
"We have not seen much evidence of aid, especially in the Uzbek neighborhoods," our correspondent said on Thursday.
Thousands of displaced people were stranded on the Kyrgyz side of the Uzbek border, unable to cross after Uzbekistan closed the border.
"We are not receiving aid. We are sleeping in the street with the children, even in the rain," Mohidil, a woman in her 40s, said near the border.
Authorities in Osh began cleaning up the streets as basic foodstuffs were being sold from lorries around the city amid a massive military presence.
But in the Uzbek village of Shark, at the entrance to Osh, the few remaining inhabitants, all men, accused authorities of giving food only to ethnic Kyrgyz.
The US has promised Kyrgystan's interim government $800,000 in emergency aid funds and has dispatched Robert Blake, its special envoy, to the country.
Blake was due in the capital Bishkek on Friday and Saturday for talks with the Kyrgyz government.
"There is in fact an emerging humanitarian crisis in Kyrgyzstan and we are prepared to respond further to that," Philip Crowley, a US state department spokesman, said.
The interim government that took office after Kurmanbek Bakiyev was deposed as president earlier this year, appears to be ill-equipped to deal with the turmoil and unable to control the south.
Kyrgyzstan's 5.3 million population is mainly made up of Kyrgyz (70%) ethnic Uzbeks (15%) and Russians (8%).
About 50% of the Osh region's 1.2 million inhabitants are ethnic Uzbeks.
About 40% of a population of one million in Jalal-abad region are ethnic Uzbeks.
It has blamed Bakiyev for hiring "provocateurs" to instigate the deadly riots and bemoaned a lack of international support, saying: "We were left alone with the enemy in the most difficult days."
Roza Otunbayeva, Kyrgyzstan's interim president, said she had "no doubt" Bakiyev was to blame.
"His sons have been discussing that they want to organise such a crisis and we thought not of such a scale and not of such a deepness," she told Al Jazeera in an interview on Tuesday.
The country's health ministry said the number of deaths from the clashes could be higher as many families were choosing to bury their dead bypassing official morgues.
The riots were the worst inter-ethnic clashes to hit Kyrgyzstan since the collapse of the Soviet Union.
Ethnic Uzbeks make up 14 per cent of the country's population of 5.3 million.