Fifteen men accused of leading popular protests in the Uzbek town of Andijan in May have pleaded guilty to multiple charges against them.
The government is accused of hiding the truth over the uprising
Prosecutors accused them of terrorism, shooting hostages and belonging to banned Islamic groups, on the first day of their trial in the capital Tashkent.
The Uzbek government says 187 people died in the uprising in Andijan.
But human rights groups say 500 or more civilians may have died and have called for an arms embargo against Uzbekistan.
The government in Tashkent has been criticised for rejecting an international investigation into the incident.
Our correspondent in Tashkent, Ian MacWilliam, says the legal proceedings are being compared to a Soviet-style show trial.
The men sat in a metal cage as the charges were read out in the courtroom, where relatives of state security personnel killed in the unrest wept as they listened.
As the trial opened, New York-based group Human Rights Watch (HRW) called on the US and the European Union to impose an arms embargo and other sanctions on Uzbekistan.
The group released a report on Tuesday documenting a "brutal" security service crackdown in which local residents were allegedly forced to make false confessions that they belonged to militant organisations and that the Andijan protesters carried weapons.
"Instead of going after the perpetrators of the massacre, the Uzbek government is trying to deny responsibility and silence witnesses," Holly Cartner, director of HRW in Europe and Central Asia, said in a statement.
The unrest began on 12 May after supporters of 23 local businessmen - on trial for alleged Islamic extremism - broke into Andijan's jail and freed them.
The armed men then occupied the town hall and a huge anti-government protest began.
Three of the Andijan businessmen - recaptured after being freed - are among the defendants to be tried by the supreme court.
Another three men are citizens of neighbouring Kyrgyzstan.
Uzbek prosecutors allege that participants in the revolt planned to overthrow the government and create an Islamic state.
Prosecutor Anvar Nabiyev told the court: "Supported by foreign forces, their task was to destabilise the situation and, finally, to set up a puppet state serving their interests."
The prosecution claims the organisers were trained in Kyrgyzstan and received funding from abroad - and say they are linked to two Islamist organisations, the Islamic Movement of Turkestan and a branch of the radical organisation Hizb ut-Tahrir.
Human rights group Amnesty International has denounced what it described as widespread persecution of eyewitnesses in order to hide the truth.
In a report, it said thousands of people had been arrested since the events in May.
"People in detention are at serious risk of being subjected to torture and other ill-treatment," Amnesty's Uzbekistan researcher Maisy Weicherding said.
Meanwhile, six US senators have written to the Pentagon asking it to withhold payment of nearly $23m (£13m) to Uzbekistan for use of an airbase.
Tashkent said in July it would no longer host US forces at the base - but the Pentagon says it will pay what it owes.
The senators said they objected to paying a regime "that has expelled our forces from its country, massacred hundreds of demonstrators at Andijan and is disregarding US concerns on a host of issues".