Thousands of protesters surged through the streets of an eastern Uzbekistani city on Friday, enraged by the government's decision to jail 23 Muslim businessmen on charges of religious extremism.

An armed crowd took over the high-security jail in Andijon shortly after midnight and released as many as several thousand prisoners.

The Uzbek human-rights group Appeal said the gunmen also seized the regional administration building, but a government spokesman denied it.

Thousands of people were said to be rallying outside the building, amid reports of gunfire between protesters and police. Several buildings were torched.

"It is not clear who is in charge of the town," said a spokesman for Appeal, Faidjahon Zainobidinov.

He said more than 2,000 prisoners were freed, but estimates from other people ranged from as little as a few dozen to more than 4,000.

President Islam Karimov flew to the city, which lies about 480 kilometres southeast of Tashkent in the Ferghana Valley.

Peaceful demonstrations have been held for weeks to demand the release of the 23 men, who are currently awaiting a verdict after a trial that ended Wednesday.

They're accused of belonging to an extremist cell that plotted to overthrow the government and establish an Islamic state.

But their defenders insist the charges were trumped-up by a government that wanted to crack down on independent-minded community leaders who might challenge its authority.

Hundreds of other men have been jailed on similar accusations in Uzbekistan recently.

Protests are rare in Andijan, a city of nearly 320,000 people. However, it lies only 40 kilometres from the border with Kyrgyzstan, where huge demonstrations forced its president to resign in March.

That coup is said to have rattled Karimov, who has been in charge of Uzbekistan since 1990, when the authoritarian state was still under Soviet control.

The country, which is largely agrarian, has a population of about 26 million.

With a report from Agence France-Presse