Ethnic Uzbek Kyrgyz pray after peace negotiations to pull down a barricade between Uzbek and Kyrgyz districts Saturday in the southern Kyrgyz city of Osh, Kyrgyzstan. Entire Uzbek neighborhoods of southern Kyrgyzstan have been reduced to scorched ruins by rampaging mobs of ethnic Kyrgyz who forced nearly half of the region’s roughly 800,000 Uzbeks to flee for their lives.

Bishkek, Kyrgyzstan ? A top U.S. envoy called Saturday for an independent investigation into the violence that has devastated southern Kyrgyzstan, as amateur video emerged of unarmed Uzbeks gathering to defend their town during the attacks.

Prosecutors on Saturday charged Azimzhan Askarov, the head of a prominent human rights group who shot the video, with inciting ethnic hatred. Askarov had accused the military of complicity in the bloody rampages that sent hundreds of thousands of Uzbeks fleeing for their lives.

The country’s rights ombudsman Tursunbek Akun insisted the charges against Askarov were fabricated, and activists in Bishkek demonstrated before U.N. offices to demand his release.

Valentina Gritsenko, head of the Justice rights organization, said she feared Askarov was being tortured. He was detained with his brother on Tuesday in his southern hometown of Bazar-Korgon, colleagues told The Associated Press.

Entire Uzbek neighborhoods in southern Kyrgyzstan have been reduced to scorched ruins by rampaging mobs of ethnic Kyrgyz who forced nearly half of the region’s roughly 800,000 Uzbeks to flee. Interim President Roza Otunbayeva says up to 2,000 people may have died in the clashes.

Kyrgyz authorities say the violence was sparked by supporters of ex-president Kurmanbek Bakiyev, who was toppled in April amid accusations of corruption. The U.N. has said the unrest appeared orchestrated, but has stopped short of assigning blame. Bakiyev, from exile, has denied any involvement.

Many ethnic Uzbeks also accused security forces of standing by or helping majority Kyrgyz mobs as they slaughtered Uzbeks and burned neighborhoods. Col. Iskander Ikramov, chief of the Kyrgyz military in the south, says the army didn’t interfere because it is not a police force.

U.S. Assistant Secretary of State Robert Blake met with Otunbayeva in Bishkek, the capital, on Saturday after touring several packed refugee camps in neighboring Uzbekistan.

Blake said the interim government should probe the violence and “such an investigation should be complemented by an international investigation by a credible international body.”

He said the U.S. was working with the Kyrgyz government to make sure the refugees would be able to return home safely. The United States has released $32.2 million in aid, and Russia and France also sent planeloads of relief gear.

The United Nations estimates 400,000 people have fled their homes and about 100,000 of them have entered Uzbekistan.