Russia sent hundreds of paratroopers to Kyrgyzstan today to protect its military facilities, Interfax reported.
It comes as ethnic clashes spread in the Central Asian state, where the death toll from days of fighting stands at 97.
Ethnic Uzbeks in a besieged neighbourhood of Kyrgyzstan's second city Osh said gangs, aided by the military, were carrying out genocide, burning residents out of their homes and shooting them as they fled.
Witnesses saw bodies lying on the streets.
Interfax news agency, citing a security source, said a battalion of Russian paratroopers had arrived in the country today to help protect Russian military facilities.
A Russian army battalion is usually around 400 men, but Interfax referred to a 'reinforced battalion', which can include as many as 650 troops.
'The mission of the force that has landed is to reinforce the defence of Russian military facilities and ensure security of Russian military servicemen and their families,' the source was quoted as saying.
Kyrgyz news website www.24.kg cited a Kyrgyz defence ministry source as saying Russian troops had landed at Kant air base aboard three Russian IL-76 aircraft.
The interim government in Kyrgyzstan, which took power in April after a popular revolt toppled president Kurmanbek Bakiyev, has appealed for Russian help to quell the riots in the south.
Bakiyev, exiled in Belarus, said Kyrgyzstan was on the verge of collapse.
‘God help us! They are killing Uzbeks like animals. Almost the whole city is in flames,’ Dilmurad Ishanov, an ethnic Uzbek human rights worker, told Reuters by telephone from Osh.
Led by Roza Otunbayeva, the interim government has sent a volunteer force to the south and granted shoot-to-kill powers to its security forces in response to the deadly riots, which began in Osh late on Thursday before spreading to Jalalabad.
The Interior Ministry said the situation in the Osh and Jalalabad regions - strongholds of Bakiyev and his family - remained 'complex and tense'.
'Residents are calling us and saying soldiers are firing at them. There's an order to shoot the marauders, but they aren't shooting them,' said ex-parliamentary deputy Alisher Sabirov, a peacekeeping volunteer in Osh.
Takhir Maksitov of human rights group Citizens Against Corruption said: ‘This is genocide.’
Earlier, Amnesty International called on Kyrgyzstan to protect its ethnic Uzbek minority from racial violence and has urged the country's neighbours to keep their borders open to refugees.
At least 82 people have been killed and more than 1,000 wounded in ethnic clashes between ethnic Uzbeks and Kyrgyz.
The interim government of Kyrgyzstan has granted its security forces shoot-to-kill powers in an effort to stop the violence.
One woman appealed for aid as she fled to neighbouring Uzbekistan, saying: 'Law enforcement is failing to effectively provide human security to its population, in particular to the Uzbek community.'
Amnesty also urged Uzbekistan to keep open its border with Kyrgyzstan to thousands of ethnic Uzbek refugees fleeing the violence, which Kyrgyz interim leader Roza Otunbayeva admitted had spiralled 'out of control'.
'With thousands of people on the move seeking safety, the authorities... of Uzbekistan in particular must keep their borders open and allow entry to all those fleeing the escalating violence in Kyrgyzstan,’ Ms Weicherding said.
