Kyrgyzstan's interim government declared a state of emergency and a curfew in southern parts of the country on Friday after deadly ethnic clashes there.
"Seven people have been killed and about 50 injured," interim government spokesman Azimbek Beknazarov told national radio.
The violence had clearly been inter-ethnic and well organised, Beknazarov added, after having visited the city. And exchanges of fire continued even after a curfew was declared.
Police were still discovering bodies in the city, said Beknazarov.
The interior ministry said five people suspected of having organised the violence in Osh had been arrested.
"The situation in Osh remains worrying," a ministry statement added.
Health officials earlier said the violence had left three people dead and 46 in hospital, of whom five were in a serious condition.
"Clashes and exchanges of fire between groups of youths took place overnight Thursday to Friday in Osh and the neighbouring districts of Karassu, Arava and Uzgen," government spokesman Farid Niyazov told AFP.
The authorities sent armoured vehicles to the scenes of the violence in a bid to restore order.
"A state of emergency has been declared in Osh and these districts from June 11 (Friday) until June 20," said Niyazov.
Interior Minister Bolot Cher and Defence Minister Ismail Issakov had both travelled to Osh, he added.
Witnesses said brawls had broken out between ethnic Kyrgyz and ethnic Uzbek groups in the city, once the stronghold of former president Kurmanbek Bakiyev, who was overthrown in April.
"About a thousand youths armed with batons and stones gathered Thursday evening in the centre of Osh," Azamat Ussmanov told AFP.
"They broke shop windows and the windows of residential buildings, burned cars. Several fires broke out in the town."
A local police spokesman said they had sent several units out to try to restore order.
Since last April's uprising, which overthrew Bakiyev and left 87 people dead, foreign and international leaders have warned of the danger of civil war in this strategically important country.
But the provisional government has struggled to establish order over the impoverished state amid ethnic clashes in the volatile south and a corruption scandal involving several high-ranking interim government officials.
The latest clashes came just a few days after the government lifted the state of emergency in the neighbouring district of Suzak.
The authorities imposed the restrictions there from May 19 to June 1 following violent demonstrations. They also cancelled the presidential election, which had been scheduled for this autumn.
In a measure of Kyrgyzstan's strategic importance, both Russia and the United States have military bases there.
The US base at Manas, outside Bishkek in the north, is a key hub for US air refueling tanker planes and for the giant transport planes that ferry US troops and supplies to and from Afghanistan.
NATO has increasingly relied on the base as 30,000 additional US forces deploy to Afghanistan.
But the US military presence has irritated Russia, placing Kyrgyzstan at the center of a big power rivalry for regional influence.
Kyrgyzstan is set to hold parliamentary elections in October as well as a referendum on a new constitution.