At least 1,400 people have been injured in the fighting, according to the country's interim government, which has struggled to stem the nation's worst ethnic violence since the collapse of the Soviet Union.
However, doctors and rights workers have warned that the real number of casualties might be much higher because ethnic Uzbeks may be too afraid to seek hospital treatment.
Meanwhile, up to 80,000 ethnic Uzbeks - mostly women and children - were reported to have crossed the border into neighbouring Uzbekistan to escape the unrest.
Most were being housed in hastily-set up camps along the border.
Refugees at border
Yves Giovannoni, the head of the International Committee of the Red Cross (ICRC) delegation in Central Asia, told Al Jazeera that reports of more people massing at the border with Uzbekistan were true although he could not confirm how many people.
"We know that definitely around 50,000 people have crossed into Uzbekistan. That more are waiting to cross. This has definitely been prompted by the heavy loss of human life, what happened in Osh and partly in Jalal'abad over the last days.
"We have heard some harrowing stories of violence, reports of severe brutality with intent to kill and this of course has frightened the people.
"So we don't know how long the flow of refugees at this point [will go on for]."
Al Jazeera's Robin Forestier-Walker, reporting from the border, said there was a steady stream of ethnic Uzbeks trying to cross, adding that violence in the city of Osh was ongoing on Sunday.
"We set out into the city earlier today but had to turn back because it was simply too dangerous," he said.
Our correspondent quoted witnesses as saying that three Uzbek neighbourhoods were under attack, but stressed that he had only been able to hear the Uzbek side.
Many of the fleeing ethnic Uzbeks accused Kyrgyz law enforcement officials of abetting gangs of ethnic Kyrgyz.
Ban Ki-moon, the UN secretary general, has expressed alarm at the scale of the fighting.
There have also been claims that Kurmanbek Bakiyev, the former Kyrgyz president who was ousted in April, has been orchestrating a campaign of ethnic conflict along with his supporters.
Michael Andersen, a Danish filmmaker who has been living in Osh, said "it's very likely that Bakiyev and his cronies are behind this".
"I lived in Osh for several years and when you live there, you don't feel any everyday tension between Uzbeks and the Kyrgyz," he told Al Jazeera.
"This is clearly something that is constructed and provoked by some third party."
Bakiyev, who is in exile in Belarus, has denied any involvement in the violence.
Kyrgyzstan's 5.3 million population is mainly made up of Kyrgyz (70%) ethnic Uzbeks (15%) and Russians (8%).
About 50% of the Osh region's 1.2 million inhabitants are ethnic Uzbeks.
About 40% of a population of one million in Jalal'abad region are ethnic Uzbeks.
Kyrgyz authorities on Sunday sent five planes of soldiers from the capital Bishkek to Jalal'abad, where the worst of the fighting appeared to be centred.
But the Kyrgyz interim government has also sought Russia's help to quell the violence, but Moscow has declined the request to send military assistance.
However, Russia sent hundreds of paratroopers to Kyrgyzstan on Sunday to protect its military facilities in the north, the Russian Interfax news agency reported.
"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," a Russian military source was quoted as saying.
The south of the former Soviet republic used to be the stronghold of the deposed president.
The country is currently led by a coalition of rival politicians that coalesced earlier this year in opposition to Bakiyev, who was deposed after anti-government protests resulted in deadly clashes.
Interim authorities had planned to hold a referendum to approve a new constitution on June 27, but the likelihood of that vote taking place looks increasingly slim.