Chechen rebel leader Shamil Basayev, who has claimed responsibility for the Beslan school hostage-taking in Russia, is not "worthy of existence," US Deputy State Secretary Richard Armitage said on Friday.

"He has proved beyond the shadow of doubt that he is inhuman," Armitage, who is on a visit to Poland, told a press conference in Warsaw.

"Anyone who would use (the killing of) innocents for political aims is not worthy of existence in the type of society that we endorse," he added.

In a statement posted Friday on a rebel website, the notorious warlord claimed responsibility for a series of recent attacks in Russia, including the school siege in southern Russia two weeks ago, in which more than 330 people were killed.

Russia's Federal Security Bureau has offered a bounty of up to 300 million rubles (over 10 million US dollars) for information that will help it hunt down Basayev and another most wanted warlord Aslan Maskhadov.