The proposed constitution would give parliament more power and set the stage for a general election in September.

Several hundred people died in clashes between ethnic Kyrgyz and Uzbeks in the south of the country earlier in June.

The interim government called Sunday's referendum after President Kurmanbek Bakiyev was overthrown in April.

Interim leader Roza Otunbayeva said the vote would go ahead and that the country's security forces could ensure a safe vote.

Kyrgyz health officials say 275 people were killed in clashes between ethnic Kyrgyz and the country's minority ethnic Uzbeks.

Thousands of homes and businesses were destroyed and hundreds of thousands of people fled the violence.

The violence has abated but the country's Uzbek and Kyrgyz populations remain deeply divided.