The trial was later adjourned indefinitely because none of the prosecution witnesses was present.
Looking frightened, and dressed in pink prison T-shirts and shorts, the first seven of up to 30,000 jailed suspects appeared in a magistrates' court in the capital, Kigali.
They were accused of taking part in the genocide of up to a million Tutsis and politically moderate Hutus between last April and June last year.
"I am going to be accused of genocide. It is true, I killed 900 people and I expect to be executed," Musoro Ndura said as he was led into the dock.
A large crowd, mainly Tutsis bereaved in the slaughter by hardline Hutus, packed the streets around the court as the defendants drove up in a pickup truck under tight security.
The first in the dock was Ngomayubu Nkulikingoma, 17, accused of killing 12 people in the commune of Butamwa on the outskirts of the capital. He pleaded not guilty and was represented by a Unicef (United Nations Children's Fund) lawyer because he is a minor.
Other defendants just answered their names read out by the state prosecutor, Silas Munyigashali. Those found guilty could face the death penalty by firing squad.
An international tribunal, to try ringleaders who planned last year's massacres, is due to start in Arusha, Tanzania, at the end of the year. Its maximum penalty will be life imprisonment.
The first of what could be a marathon series of trials began almost seven hours late.
The official reason was that the prison vehicle transporting the eight defendants - one faced the lesser charge of stealing state funds - had broken down. But prison officials said privately they had been waiting for high-level approval for the trials to proceed. Political analysts said the government, headed by the Hutu President Pasteur Bizimungu but backed by a Tutsi-dominated army, appeared divided over the timing of the trials.