In a letter published by leading rebel websites, he said a suicide battalion had carried out the Beslan attack.
The letter also claimed bomb attacks on two Russian airliners and a Moscow metro station this summer.
Russia is offering $10m for the capture of Mr Basayev, whose reported actions a US official described as “inhuman”.
Aslan Maskhadov, the main Chechen rebel leader, has denied any links to the three-day siege in the North Ossetian town which ended in carnage.
