ANDIJAN, Uzbekistan -- Thousands of terrified Uzbeks trying to flee into Kyrgyzstan burned a government building Saturday and attacked border guards, a second day of violence triggered by a brazen jailbreak to free accused Islamic militants and a massive demonstration against economic conditions under the iron-fisted rule of President Islam Karimov.

There was no immediate word on casualties in the latest violence in the former republic of the ex-Soviet Union, but witnesses to Friday's mayhem said more than 200 people were killed in gunfire after government troops confronted the huge demonstration.

Andijan is Uzbekistan's fourth-largest city, about 30 miles from the country's easternmost border in the narrow finger of territory that protrudes deep into Kyrgyzstan, where an uprising in late March ousted that country's only post-Soviet leader.

The Uzbek unrest began overnight Friday when protesters freed as many as 2,000 prisoners, including the 23 members of the Akramia Islamic group on trial on charges of being members of a group allied with the outlawed radical Islamic party Hizb-ut-Tahrir. It seeks to create a worldwide Islamic state and has been forced underground throughout most of Central Asia and Russia.

Karimov's hardline secular regime has a long history of repressing Muslims who worship outside state-approved mosques.

On Friday, thousands of people swarmed into the streets of Andijan, clashing with police and seizing the administration building, which was later taken back by government forces. Demonstrators did not call for the ouster of Karimov but instead complained bitterly about the dire economic conditions.

Russian President Vladimir Putin telephoned Karimov on Saturday to express concern that the violence could destablize Central Asia, the Kremlin press service said in a statement.

The U.S.-allied Uzbek leader blamed the fighting on Islamic extremists. During a news conference in the capital, Tashkent, he said 10 government troops and "many more" militants died in the fighting Friday. At least 100 people were wounded, Karimov said without specifying who started the shooting.

Uzbekistan has a U.S. air base in the Karshi-Khanabad region, 90 miles from the Afghan border, to support military operations in that country after the Sept. 11 attacks in the United States. The number of troops there has reached several thousand at times. The base is more than 430 miles southwest of Andijan.

The White House on Saturday declined to comment, although press secretary Scott McClellan on Friday urged both the government and demonstrators to "exercise restraint."

After the shooting in Andijan on Friday, Lutfulo Shamsutdinov, head of the Independent Human Rights Organization of Uzbekistan, said he saw the bodies of about 200 victims being loaded onto trucks near the square. A witness in central Andijan told The Associated Press that "many, many dead bodies are stacked up by a school near the square."

Disturbances flared Saturday in the village of Korasuv, 30 miles to the east, when 6,000 Uzbeks trying to flee into Kyrgyzstan were blocked at the border. Some in the group set fire to a police station, vandalized police cars and attacked border personnel, a Kyrgyz official said. Uzbek helicopters were seen circling overhead.

In Andijan, hundreds of angry protesters gathered Saturday at the site of Friday's bloodshed, placing six bodies on display from the scores witnesses said were killed in fighting. Clusters of bystanders watched as men covered other bloodied bodies with white shrouds.

Demonstrators, some with tears in their eyes, condemned the government for firing on women and children. Residents said a group of hundreds later went to a local police station to confront the heavily armed authorities, who sent a helicopter buzzing low over the crowd to scare them away.

Karimov said he ordered authorities not to take any physical action against the demonstrators Saturday.

"In Uzbekistan, nobody fights against women, children or the elderly," he said.

An Andijan resident reached by telephone said Sunday that the city had been largely quiet overnight, aside from a volley of gunfire that lasted a few minutes. The resident, who spoke on condition of anonymity, said protesters had left the square at the center of the uprising and that the streets were still full of government soldiers.

In Friday's standoff, Karimov claimed the government had offered the demonstrators free passage out of the city in buses with their weapons, seized in attacks on a police station and military outpost.

But a protest leader, Kabuljon Parpiyev, said Interior Minister Zakir Almatov did not sound willing to negotiate when they spoke by phone Friday.

"He said, 'We don't care if 200, 300 or 400 people die. We have force and we will chuck you out of there anyway,"' Parpiyev quoted Almatov as saying.

Earlier Saturday, soldiers loaded scores of bodies onto four trucks and a bus after blocking friends and relatives from collecting them, witnesses said.

Daniyar Akbarov, 24, joined the protests Saturday after being freed from the prison during the earlier clashes.

"Our women and children are dying," he said, tearfully beating his chest with his fists. Akbarov said he saw at least 300 people killed.

The focus of the jailbreak was 23 men charged with membership in a group allegedly allied with Hizb-ut-Tahrir.

The men are alleged members of Akramia -- a group named for their founder, Akram Yuldashev, an Islamic dissident sentenced in 1999 to 17 years in prison for allegedly urging Karimov's ouster. He has proclaimed his innocence. The group forms the heart of the city's small business community.

The trial of the 23 has inspired one of the largest public shows of anger at the government in years, and the largest outbreak of violence since Uzbekistan became an independent country after the 1991 Soviet collapse.

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Associated Press reporter Burt Herman contributed to this report from Tashkent.