Kyrgyzstan appealed for Russian help on Saturday to stop ethnic fighting that killed at least 63 and left parts of its second-largest city in flames, the worst violence since the president was toppled in April.

The interim government in Kyrgyzstan, which hosts US and Russian military bases, said it was powerless to stop armed gangs from burning down the homes and businesses of ethnic Uzbeks in parts of Osh. Gun battles raged throughout the night.

"We need the entry of outside armed forces to calm the situation down," interim government leader Roza Otunbayeva told reporters. "We have appealed to Russia for help and I have already signed such a letter for President Dmitry Medvedev."

Kyrgyzstan, a poor ex-Soviet state of 5.3 million people, declared a state of emergency in Osh and several rural districts early on Friday after rival ethnic gangs fought each other with guns, iron bars and petrol bombs.

Renewed turmoil in Kyrgyzstan will fuel concern in Russia, the US and neighbor China. Washington uses an air base at Manas in the north of the country, about 300 km (190 miles) from Osh, to supply its forces in Afghanistan.

Russian Prime Minister Vladimir Putin and Otunbayeva discussed the situation in a telephone call on Saturday, the Russian government's press service said, without giving details.

A spokeswoman for the Kyrgyz Health Ministry said at least 63 people had been killed and 835 wounded in the violence, which is taking place in the southerly power base of former president Kurmanbek Bakiyev, deposed in April by a popular revolt.

Referendum plan

Otunbayeva accused supporters of Bakiyev - like her, an ethnic Kyrgyz - of stoking the violence to disrupt her government's plans to hold a national referendum on June 27 to vote on changes to the constitution.

"This event shows that the push by these people to turn backwards is extraordinarily great," she said.

She added more reinforcements would be sent to Osh. The interim government has already deployed troops and armored vehicles and declared a night-time curfew in Osh, to no avail.

A Reuters correspondent in Osh said gun battles were still taking place in an Uzbek neighbourhood. Gas was shut off to Osh and some neighborhoods had no electricity.

"Everywhere is burning: Uzbek homes, restaurants and cafes. The whole town is covered in smoke," said local human rights worker Dilmurad Ishanov, an ethnic Uzbek.

"We don't need the Kyrgyz authorities. We need Russia. We need troops. We need help."

The European Union said it would send its special representative for Central Asia, Pierre Morel.

Asked about possible Russian help, an EU spokesman said: "We would welcome any effort from one of our international partners to help the situation in Kyrgyzstan."

Otunbayeva said Osh was also facing a humanitarian crisis as food was running out. She said her government had decided to open the border to Uzbekistan to allow fleeing Uzbeks to escape, although it was not clear who controlled the frontier.

One witness said some women and children had made it across to the Uzbek town of Marhamat, 60 km (38 miles) from Osh, and camps had been set up for those without family in Uzbekistan.

Cholponbek Turuzbekov, deputy commander of the Kyrgyz border service, said people were crossing into Uzbekistan, but that he did not know how many people had done so.

ETHNIC VIOLENCE

Kyrgyzstan, which won independence with the collapse of the Soviet Union in 1991, has been in turmoil since the revolt that toppled Bakiyev on April 7, kindling fears of civil war.

Supporters of Bakiyev, now in exile in Belarus, briefly seized government buildings in the south on May 13, defying Otunbayeva's central authorities in Bishkek.

The latest clashes are the worst ethnic violence since the bloodshed in 1990, when then-Kremlin leader Mikhail Gorbachev sent in Soviet troops after hundreds of people were killed in clashes between Kyrgyz and Uzbeks in and around Osh.

Kyrgyzstan and Uzbekistan intertwine in the Fergana Valley. While Uzbeks make up 14.5 percent of the Kyrgyz population, the two groups are split roughly equally in the Osh region.

Last May 19, two people were killed and 74 wounded in clashes between Kyrgyz and Uzbeks in the city of Jalalabad. On the same day, Otunbayeva said she would rule until the end of 2011, scrapping plans for presidential polls in October.

Her interim government now faces a major test in trying to reassert control, said Lilit Gevorgyan at IHS Global Insight:

"The explosive combination of a counter-revolution and an ethnic conflict poses the greatest threat to the future of the Kyrgyz revolution."-Reuters