MOSCOW — President Islam A. Karimov of Uzbekistan on Saturday defended the harsh crackdown on a violent uprising that had engulfed an eastern city the day before, even as new protests unfolded and hundreds of residents in the region fled to the country's border with Kyrgyzstan.

He said that 10 federal soldiers had died and that "many more rebels" had been killed on Friday in clashes in the city of Andijon, a regional capital in the country's east.

Karimov, who has ruled the Central Asian republic with an iron grip since it gained its independence from the Soviet Union in 1991, made no mention of the civilian casualties.

Others, including opposition leaders, said that scores had been killed when troops opened fire on thousands of protesters who assembled in Andijon's central square after the storming of the prison.

The various reports said the dead — which were put at 200 to 300 or more — included many civilians.

But the reports were varied and numerous, and few details were verifiable. Foreign journalists in the city were ordered to leave it.

New clashes erupted Saturday in the town of Karasu on the Kyrgyz border, where hundreds of Uzbeks gathered, apparently hoping to leave the country.

Protesters clashed with the police and border guards, occupying several government buildings, the Associated Press reported.

A correspondent with Kyrgyzstan's official news agency, Kabar, said that Uzbek border forces appeared to have abandoned their posts; several cars and buildings were ablaze.

"There is no control there," the correspondent, Kamil Toktorov, said in a telephone interview from Osh, Kyrgyzstan, after visiting the border.

In Moscow, the Kremlin reported that President Vladimir V. Putin and Karimov discussed the situation by telephone on Saturday — a sign of the seriousness of the events in the remote provincial city.

The Kremlin said that Putin and Karimov expressed "serious concern" over the risk of destabilization in Central Asia.

Karimov, making his first public remarks on the unfolding crisis, blamed Islamic extremists for the violence, claiming that they want to overthrow the country's secular government and impose one ruled by Islamic law.

"Their aim is to unite the Muslims and establish a caliphate," Karimov said of militants who stormed Andijon's prison early Friday, the Russian news agency Interfax reported from the Uzbek capital, Tashkent.

"Their aim is to overthrow the constitutional regime," he said.