[For more on this event, see RFE/RL's dedicated webpage Unrest in Uzbekistan]
The protesters include relatives of those injured and killed in Andijon yesterday. They angrily condemned security forces for firing on women and children.
RFE/RL correspondent Sadriddin Ashurov, who was in the city, said people were searching for bodies.
"I am walking near the regional administration building right now, there are a lot of people from Andijon gathering there," Ashurov reported. "They express their strongest discontent. They talk about yesterday's events, about shooting peaceful people, including children and women, they say they [government troops] did not show mercy to anyone. People are bringing bodies, corpses to the statue of [Uzbek poet] Bobur. They are putting bodies wrapped in bedsheets in a row next to the statue."
It's unclear how many people have died in Andijon, which is now sealed off by Uzbek security forces.
The violence began early yesterday when armed supporters of a group of men on trial for Islamic extremism charges broke into the jail where the men were being held.
Protesters then took over the regional-administration building and demanded the release of all people jailed as suspected members of an Islamic group, Akramiya, including the group's founder, Akram Yuldoshev.
At least nine people were killed in the initial clashes. But many more were feared to have been killed later that day, when security forces opened fire on a crowd protesting for better living conditions and the resignation of President Islam Karimov.
A doctor at a local hospital told the AFP news agency this morning that more than 50 people had been killed. Reports spoke of some dead bodies still lying in the streets.
But the situation is unclear. And now correspondents have been forced to leave Andijon.
Uzbekistan's President Islam Karimov was due to hold a press conference today about the events in Andijon. But as yet there's been no information.
Meanwhile, reports say as many as a thousand people have gathered at the border with Kyrgyzstan. Protesters reportedly took the mayor of the Kyrgyz town of Kara-suu hostage.
At the White House last night, spokesman Scott McClellan called for restraint. "We urge both the government and the demonstrators to exercise restraint at this time," he said. "The people of Uzbekistan want to see a more representative and democratic government, but that should come through peaceful means, not through violence."
Russian Foreign Minister Sergei Lavrov said yesterday that the conflict was an internal affair of Uzbekistan. "First of all, this is Uzbekistan's internal affair," he said. "We are monitoring closely the information that we are receiving from that country. Our latest information suggests that the situation is stabilizing."
In other international reactions, the European Union yesterday blamed the conflict on Karimov's government. It said it had not paid what it called "sufficient attention" to the country's problems with human rights, the rule of law, and poverty.
But the Organization for Security and Cooperation in Europe (OSCE) has so far declined to comment. The OSCE representative in Vienna told RFE/RL yesterday that the organization's office in Tashkent was monitoring the situation.
(By Gulnoza Saidazimova)See also:
Bloody Friday In The Ferghana Valley
Several Dead After Violent Day In Uzbek City
Protesters Charge Officials With Using Extremism Charges To Target Entrepreneurs
Analysis: Police Crush Protest In Tashkent
Analysis: Economic Concerns Primary In Andijon
Background: Banned Hizb ut-Tahrir Faces Dwindling Appeal, Internal Divisions
Interview: Opposition Leader Tells RFE/RL About 'Farmers' Revolution'