In the letter, the spokesman stated that Ilyas Kashmiri, along with his associates, was killed on June 03 in US drone strike in South Waziristan.
"We confirm that our Amir (leader) and commander in chief, Mohammad Ilyas Kashmiri, along with other companions, was martyred in an American drone strike on June 3, 2011, at 11:15p.m.," Abu Hanzla Kashir, who identified himself as an HuJI spokesman, said in a statement faxed to media.
"God willing ... America will very soon see our full revenge. Our only target is America."
The authenticity of the statement could not be verified.
U.S. and Pakistani officials have not confirmed his death yet.