UN agencies said they feared an escalation in fighting in Kyrgyzstan, warning of an "ethnic tinderbox" after several hundred people were killed and an estimated 275,000 fled their homes.
UN relief agencies and the International Committee of the Red Cross (ICRC) stepped up deliveries of medical aid, food and shelter to Kyrgyzstan and neighbouring Uzbekistan as supplies in some areas were running low.
The ICRC said in a statement after visiting one of the towns at the heart of the violence that "several hundred people have been killed in the fighting," although it was too early to say how many.
A Kyrgyz health ministry toll had earlier put the number of dead at 170. ICRC spokesman Christian Cardon said at the agency's headquarters in Geneva: "We saw that there were more than that when we visited the morgue at Osh, amongst others."
The office of the UN High Commissioner for Refugees (UNHCR) said it would begin airlifting some 240 tonnes of shelter equipment to Uzbekistan on Wednesday from a warehouse in Dubai.
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"We are alarmed by the rapid escalation of violence since 10 June in southern Kyrgyzstan, which has left scores of people dead and led to the displacement of an estimated 200,000 people within the country in addition to 75,000 who have sought safety in Uzbekistan," said UNHCR spokesman Andrej Mahecic.
Kyrgyzstan's interim leader Roza Otunbayeva said on Tuesday that the inter-ethnic clashes were waning.
Aid workers reported sporadic fighting in the Osh and Jalalabad, close to the Uzbek border.
"We fear that unless peace and order is restored swiftly more people could be displaced as they flee to the countryside or try to cross the border to Uzbekistan," Mahecic told journalists.
The office of the UN High Commissioner for Human Rights said its staff had gathered evidence from witnesses suggesting that the violence was deliberately triggered by armed men in five simultaneous attacks in Osh last Thursday.
"We believe this is an extremely dangerous situation given the ethnic patchwork in this part of Kyrgyzstan, it's a highly complex ethnic mix there with some 80 ethnic groups just in the Osh region," said spokesman Rupert Colville.
"It has been known for many years that this region is a potential ethnic tinderbox, for that reason it's essential that the authorities act firmly to halt the fighting."
"We have strong indications that this event was not a spontaneous inter-ethnic clash, we have some indications that it was to some degree orchestrated, targeted and well planned," Colville added.
