Kyrgyzstan's interim government yesterday promised a US envoy it would probe deadly ethnic clashes as it extended a state of emergency amid fears of fresh violence in the volatile south.

Officials and aid agencies say the clashes between Kyrgyz and Uzbeks have killed up to 2,000 people and affected up to one million, including 300,000 people displaced in Kyrgyzstan and 100,000 who have fled to neighbouring Uzbekistan.

The government said yesterday it was extending a state of emergency in the violence-torn southern city of Osh and nearby areas to Friday. Imposed on June 11, the state of emergency was due to expire today.

The UN meanwhile said it was stepping up aid to the region after issuing an urgent appeal for humanitarian assistance.

After meeting with Kyrgyzstan's acting government, US Assistant Secretary of State for South and Central Asian Affairs Robert Blake said he had been promised authorities would investigate the violence.

"Members of the provisional government assured me of their intention to launch an investigation into the causes of the violence... Such an investigation should be complemented by an international investigation by a credible international body," Blake told journalists in Bishkek.

"Is it important for the provisional government to establish an atmosphere of trust and security so the refugees in Uzbekistan and the internally displaced persons in Kyrgyzstan can feel confident that they can return to their homes," he said.

Kyrgyzstan's interim leader Roza Otunbayeva admitted last Friday that the death toll from the clashes was probably 2,000 - 10 times the official estimate of 192.

The World Food Programme said yesterday it would step up its aid to the region and from today will airlift 110 tonnes of high energy biscuits from its warehouse in Dubai to Osh and to Andijan in Uzbekistan.

"With a huge number of people displaced by the conflict, and thousands more trapped without food, water or supplies, there's not a moment to lose," the UN agency's executive director Josette Sheeran said in a statement.

UN chief Ban Ki-moon said last Friday the UN was launching a $71-million humanitarian appeal for Kyrgyzstan and that a separate appeal for Uzbekistan would be launched this week.

Ban cited "shortages of food, water and electricity in the affected areas, due to looting, lack of supply, and restrictions on movement" and said hospitals were running low on medical supplies.

In Osh, residents said they were bracing for new violence after Otunbayeva promised that makeshift barricades around Uzbek neighbourhoods would be removed.

Roads leading to most of the city's Uzbek districts remained closed off with cut-down trees, burnt-out cars and storage containers.

"If they come to open the access roads they will shoot at us again. The army is against us, the state is fighting against us," said 63-year-old Pulat Shikhanov.

"We are not expecting anything good from this. This will restart until they've chased out all the Uzbeks," said the head of the local district, Purdubai Barubayev.

The mayor of Osh, Melisbek Myrzakmatov, told journalists that authorities had set a deadline of 2 p.m. today for the barricades to be removed.

"We gave them two days to remove the barricades. If they do not remove them, we will resort to force," he said.

"We don't want to touch (the Uzbeks) but you know they have a lot of weapons and Kyrgyz hostages," he added.

The riots were the worst inter-ethnic clashes to hit the impoverished Central Asian state since the collapse of the Soviet Union.

Victims of the unrest said the violence was a brutal and orchestrated campaign by armed militias of ethnic Kyrgyz targeting Uzbeks, who make up 14 per cent of Kyrgyzstan's population of 5.3 million.

Kyrgyzstan's interim government has accused former president Kurmanbek Bakiyev, who was ousted in violent street protests in April, of hiring "provocateurs" to instigate the deadly riots. Bakiyev has denied any involvement.

Kyrgyzstan prosecutors yesterday said they had charged a human rights activist with inciting violence during the clashes, but rights groups said he was being persecuted for documenting the unrest.